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Biomedical subjects

Ryo Yoshida

Publications and source records attributed to Ryo Yoshida.

At least 19 recordsLinked to original sources
PubMed2006

Maskless microfabrication of thermosensitive gels using a microscope and application to a controlled release microchip.

Here we show a simple and convenient method to prepare micropatterned gels by the use of a microscope, without large-scale or special-order experimental setup. UV light focused by an objective lens was locally irradiated to a pre-gel solution in a microchannel. This method would be useful for preparing microgels at target positions in microchips. A controlled drug-release microchip has actually been fabricated by utilizing this local photo-irradiation method, and pulsatile drug release in response to temperature changes was demonstrated.

Journal Article↗
PubMed2006

Dependence of turbidity oscillations of self-oscillating polymers on the selective recognition of the crown ether receptors contained in the polymer chain.

The turbidity oscillations of self-oscillating polymers in the Belousov-Zhabotinsky (BZ) reaction system depending on the crown ether receptors contained in the polymer network have been studied. The three monomers are copolymerized, namely, N-isopropylacrylamide, the metal catalyst monomer for the BZ reaction, and the crown ether receptor monomer, to prepare the self-oscillating polymers used in this study. The turbidity oscillations are characterized by monitoring the transmittance of the polymer solution in the BZ reaction system at a specific wavelength of 570 nm. The oscillations are varied by crown ether receptors used in the polymerization process, i.e., BCAm(6) or BCAm(5), for the selective recognition of specific cations between potassium and sodium ions in the solution. The selective recognition of the BCAm receptors in the polymer chain for the two ions has brought out a variation in the turbidity oscillations by a change in the hydrophilicity of the polymer chain. The oscillations of the polymer solution composed of the BCAm(5) receptor are more influenced by sodium ion, while the polymer solution of BCAm(6) receptor is affected by potassium ion. However, the oscillation patterns of the redox changes obtained by these solution systems look much alike despite the differences in the polymer chain by crown ether receptors and cations of bromate used for the BZ reaction.

Crown Ethers↗
PubMed2006

ArrayCluster: an analytic tool for clustering, data visualization and module finder on gene expression profiles.

SUMMARY: One of the significant challenges in gene expression analysis is to find unknown subtypes of several diseases at the molecular levels. This task can be addressed by grouping gene expression patterns of the collected samples on the basis of a large number of genes. Application of commonly used clustering methods to such a dataset however are likely to fail owing to over-learning, because the number of samples to be grouped is much smaller than the data dimension which is equal to the number of genes involved in the dataset. To overcome such difficulty, we developed a novel model-based clustering method, referred to as the mixed factors analysis. The ArrayCluster is a freely available software to perform the mixed factors analysis. It provides us some analytic tools for clustering DNA microarray experiments, data visualization and an automatic detector for module transcriptional of genes that are relevant to the calibrated molecular subtypes and so on.

Bayes Theorem↗
PubMed2006

AFM observation of immobilized self-oscillating polymer.

Various types of nanocomponents have been developed to construct a nanodevice or nanomachine. Here, we add a new nanocomponent that has the function of self-oscillation. A thermoresponsive polymer carrying a Ru complex, a catalyst of the Belousov-Zhabotinsky reaction, was synthesized and immobilized on a glass plate. Periodic turbidity changes in the aqueous solution of the polymer were observed, and nanoscale self-oscillation of the immobilized polymer was observed by a scanning probe microscope.

Catalysis↗
PubMed2005

Self-oscillating soluble-insoluble changes of a polymer chain including an oxidizing agent induced by the Belousov-Zhabotinsky reaction.

A new type of self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky reaction. In this study, capture sites with a positive charge for an oxidizing agent as a counterion were incorporated into the copolymer of N-isopropylacrylamide and the ruthenium complex as a catalyst. Soluble-insoluble self-oscillation of the polymer was first achieved without adding an oxidizing agent. The effect of temperature on the self-oscillating behavior was investigated. It was clarified that the polymer had two advantageous characteristics because of the higher LCST; one is to enable self-oscillation around body temperature, and the other is to cause the oscillation for a longer time without intermolecular aggregation among the polymer chains in the reduced state. This achievement of self-oscillation of polymer chains including an oxidizing agent may lead to their practical use under oxidant-free conditions.

Acrylamides↗
PubMed2005

Control of oscillating behavior for the self-oscillating polymer with pH-control site.

A novel self-oscillating polymer was prepared by copolymerizing the catalyst for the Belousov-Zhabotinsky reaction with N-isopropylacrylamide. Further, by introducing acrylamide-2-methylpropane sulfonic acid (AMPS) with a sulfonic acid group as a pH-control site into the polymer, self-oscillation under acid-free conditions was achieved. The period and amplitude for the self-oscillation is controllable by changing the composition of the polymer. On-off switching of self-oscillation is also possible by changing temperature or substrate concentrations. The AMPS plays an important role not only to control the pH but also to change the solubility of the polymer.

Journal Article↗
PubMed2005

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions.

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.

2,2'-Dipyridyl↗
PubMed2005

Dancing waves in reaction-diffusion systems.

The mechanism of pattern formation in reaction-diffusion systems is treated as an interesting subject, generally for understanding self-organization observed in living systems and natural phenomena. Several spatial patterns appear in the reaction-diffusion systems where an activator and an inhibitor coexist as an intermediate, as represented by a traveling wave, a stationary wave called a Turing structure, etc. Here, we show new kinds of waves in reaction-diffusion systems, which exhibit reciprocating motion without colliding into each other or blinking periodically. These patterns have never been observed in the conventional numerical models, although experimentally oscillating spots have been often observed. Our model demonstrates that other than the ratio of diffusion coefficients for both intermediates, the thickness of reaction media acts to generate inhibitory effect. The spatial factor of the medium contributes to new pattern formation in reaction-diffusion systems. For the design of new functional materials, the concept might be useful as a simple controlling method for pattern dynamics.

Journal Article↗
PubMed2005

Estimating time-dependent gene networks from time series microarray data by dynamic linear models with Markov switching.

In gene network estimation from time series microarray data, dynamic models such as differential equations and dynamic Bayesian networks assume that the network structure is stable through all time points, while the real network might changes its structure depending on time, affection of some shocks and so on. If the true network structure underlying the data changes at certain points, the fitting of the usual dynamic linear models fails to estimate the structure of gene network and we cannot obtain efficient information from data. To solve this problem, we propose a dynamic linear model with Markov switching for estimating time-dependent gene network structure from time series gene expression data. Using our proposed method, the network structure between genes and its change points are automatically estimated. We demonstrate the effectiveness of the proposed method through the analysis of Saccharomyces cerevisiae cell cycle time series data.

Algorithms↗
PubMed2004

Unusual variant of the extensor carpi radialis brevis muscle: a case report.

A variation of the extensor carpi radialis brevis muscle (ECRB) origin was discovered during a cadaveric dissection. The identified ECRB originated from the fascia/tendon of the extensor digitorum communis (EDC), without any of its origin at the usual location on the lateral epicondyle. The ECRB tendon inserted onto the third metacarpal base. A branch of the posterior interosseous nerve innervated the ERCB. This is the first report of an ECRB originating from the EDC fascia/tendon. This unique variation of the ECRB origin may be of clinical interest, especially in the treatment of lateral epicondylitis (tennis elbow).

Cadaver↗
PubMed2004

A mixed factors model for dimension reduction and extraction of a group structure in gene expression data.

When we cluster tissue samples on the basis of genes, the number of observations to be grouped is much smaller than the dimension of feature vector. In such a case, the applicability of conventional model-based clustering is limited since the high dimensionality of feature vector leads to overfitting during the density estimation process. To overcome such difficulty, we attempt a methodological extension of the factor analysis. Our approach enables us not only to prevent from the occurrence of overfitting, but also to handle the issues of clustering, data compression and extracting a set of genes to be relevant to explain the group structure. The potential usefulness are demonstrated with the application to the leukemia dataset.

Algorithms↗
PubMed2003

Self-sustaining peristaltic motion on the surface of a porous gel.

We report the structural color behavior of a periodic ordered mesoporous gel synchronized with the Belousov-Zhabotinsky (BZ) reaction. The structural colored concentric rings which were spatiotemporally spread out on the porous gel were observed during the BZ reaction. The color tone of the structural color, which is determined by the swelling ratio of the gel, was periodically changed. This is the first evidence that a self-sustaining peristaltic motion occurs on the surface of a gel.

Journal Article↗
PubMed2003

Motion and morphology of the thumb metacarpophalangeal joint.

PURPOSE: To determine the variability in the flexion/extension motion of the thumb metacarpophalangeal (MCP) joint in a normal volunteer population and to determine any correlation between the shape of the thumb metacarpal head, gender, age, thumb interphalangeal (IP) joint range of motion (ROM), and thumb MCP joint ROM in a population of fresh-frozen cadaver arms. METHODS: The ROM of the thumb MCP joints of 100 volunteers (200 thumbs) was measured. The thumb MCP joints of 70 fresh-frozen cadaver arms were examined. Posteroanterior and lateral radiographs were taken of 64 MCP joints. Passive flexion and extension at the MCP and IP joints were measured with a standard goniometer starting at neutral (0 degrees ) with the metacarpal, proximal, and distal phalanges axially aligned. The distance from the volar to the dorsal edge of the articular surface (A) and the radius of curvature of the articular surface (r) of the metacarpal head were measured on the lateral view. The shape of the metacarpal head was given a value using the A/r ratio. Regression analysis was used to determine the correlation between the head shape and joint motion. The thumbs were categorized into a round group (A/r ratio > 1.7) or a flat group (A/r ratio of < 1.7) to facilitate statistical analysis. RESULTS: The volunteer population mean thumb MCP maximum flexion was 77 degrees range, 40 degrees -126 degrees ). Range of motion in hyperextension varied from 0 degrees to 72 degrees, with a mean of 35 degrees. Total ROM was from 55 degrees to 176 degrees, with a mean of 110 degrees. In the cadaver population studied the average MCP joint ROM was 94 degrees (mean flexion, 70 degrees; mean extension, 24 degrees ). The A/r ratio had a range of 1.1 to 2.2. There were 37 round and 27 flat thumb metacarpal heads. Regression analysis showed a significant correlation between metacarpal head shape and ROM; MCP joints with rounder metacarpal heads had greater motion. Round and flat metacarpal heads had significantly different motion arcs averaging 106 degrees and 77 degrees, respectively. Female gender was associated both with significantly greater MCP joint ROM (99 degrees women/87 degrees men) and a significantly higher incidence of round metacarpal heads (66% of women/36% of men). No significant correlation existed between specimen age, MCP, and/or IP joint ROM. CONCLUSIONS: There is a wide range in the magnitude of the thumb MCP joint ROM and the normal shape (round vs flat) of the thumb metacarpal head. A rounder thumb metacarpal head has greater thumb MCP joint ROM than a flatter thumb metacarpal head. Clinically we have found this information helpful in predicting posttraumatic recovery of thumb MCP joint ROM and selecting candidates for and predicting patient satisfaction with thumb MCP joint arthrodesis.

Adolescent↗
PubMed2003

Anatomy and pathomechanics of ring and small finger carpometacarpal joint injuries.

PURPOSE: The purpose of this study was to detail the pathomechanics and pathoanatomy of fracture dislocations of the ring finger and small finger carpometacarpal (CMC) joint by duplicating the pathomechanics of the fist blow. METHODS: A custom-made jig was used to position 20 fresh-frozen cadaver upper extremities in forearm neutral rotation, 90 degrees of elbow flexion, 20 degrees of wrist extension, and 20 degrees and 30 degrees of flexion at the ring and small finger CMC joint, respectively. First 7.7 kg of weight were dropped from a height of 0.76 m to 1.1 m to axially load the ring and small metacarpal (MC) heads through a custom-made apparatus. Fluoroscopic examination before and after loading, and detailed dissection after loading, were used to identify any osseous and/or ligamentous injuries. RESULTS: The most common fractures were a dorsal capitate fracture and a middle MC dorsal base fracture. The most common combinations of fractures were the dorsal capitate and dorsal hamate fractures. Multiple fractures often were identified in a number of locations including dorsally: the capitate, hamate, and index through small metacarpal bases, and volarly: the hook of the hamate and the middle through the small MC bases. CONCLUSIONS: The patterns of injuries encountered at the ring and small CMC joints can be explained by the direction and force of the applied load, position of the CMC joint at the time of loading, and the constraints imposed by specific CMC ligaments. A detailed analysis of the fracture patterns and associated ligament anatomy suggests that the typical ring and small carpometacarpal fracture dislocations are a more complex combination of fractures than identified by plain radiographs alone. The complexity of these injuries is greater than previously recognized and is most likely the result of a combination of axial load and shear stresses resulting in carpal fractures and ligament avulsions as well as fracture dislocations. This study suggests that computed tomography may be the preferred diagnostic imaging method for complete assessment of these injuries.

Aged↗
PubMed2002

Self-oscillation of polymer chains with rhythmical soluble-insoluble changes.

Self-oscillation of polymer chains in an aqueous solution has been achieved. The ruthenium catalyst for the Belousov-Zhabotinsky reaction was polymerized by using N-isopropylacrylamide and dissolved into the solution containing the BZ substrates. Periodical soluble-insoluble changes of the polymer chain were spontaneously induced by the BZ reaction. The conformational oscillations of the polymer were measured as the optical transmittance changes of the solution. This is the first report that rhythmical and reversible soluble-insoluble changes of polymer chains are realized under constant and homogeneous conditions. The transducing system from chemical energy of the BZ reaction to optical information has been constructed.

Acrylamides↗
PubMed2002

Pseudomyxoma peritonei of appendiceal cancer with metastasis to the stomach: report of a case.

Appendiceal cancer associated with pseudomyxoma peritonei is a relatively low-grade malignancy rarely associated with extraperitoneal metastasis. We report herein the case of a 71-year-old man in whom a metastasis was found in the stomach 2 years after he underwent surgery for pseudomyxoma peritonei of appendiceal cancer. He was referred to our hospital after presenting with anorexia and vomiting. Gastrofiberscopy, abdominal computed tomography, and ultrasound examination all revealed a mass 4 x 4cm in size, containing a small ulcer, in the antrum of the greater curvature of the stomach. The histopathological diagnosis made from a biopsy of the tumor was mucinous cystadenocarcinoma. A distal partial gastrectomy was performed and the resected specimens from the appendiceal cancer resected 2 years earlier showed the same histological pattern as that of the gastric lesion. To the best of our knowledge, this is only the second report of pseudomyxoma peritonei secondary to mucinous cystadenocarcinoma of the appendix that metastasized to the stomach.

Aged↗
PubMed2002

Changing site distribution of colorectal cancer in Japan.

PURPOSE: In North America and other high-risk areas, there has been a proximal shift in the subsite distribution of colorectal cancer. We wanted to determine whether any similar change has occurred in Japan, and where the incidence of this disease has increased sharply. METHODS: Data from the Reports of the Japanese Society for Cancer of the Colon and Rectum were used to analyze the time trend of colorectal cancer in Japan between 1974 and 1994 according to the patients' age at diagnosis and sex, and the site of the tumor within the colon or rectum. RESULTS: The percentage of patients over the age of 70, especially females, increased. The increase in the percentage of right-sided colon cancer in colorectal cancer cases was accompanied by a continuous decline in the percentage of rectal cancer in both sexes at all ages. In general, the percentage of right-sided colon cancer in colon cancer cases was stable in men, but increased in women. The rate among patients older than 70 years increased in men, but predominated and remained stable in women. No proximal shift in colon cancer was found in either sex under the age of 69. CONCLUSION: These findings indicated that a proximal shift in the subsite distribution of colorectal cancer has occurred in Japan. This rightward shift of colorectal cancer is due to the decreasing proportion of rectal cancer. Furthermore, the increasing proportion of older patients, especially females, may be another major determinant of the changing colon cancer subsite distribution.

Aged↗