Biomedical subjects

Shiro Usui

Publications and source records attributed to Shiro Usui.

14 recordsLinked to original sources

PubMed2006

Customizable neuroinformatics database system: XooNIps and its application to the pupil platform.

The developing field of neuroinformatics includes technologies for the collection and sharing of neuro-related digital resources. These resources will be of increasing value for understanding the brain. Developing a database system to integrate these disparate resources is necessary to make full use of these resources. This study proposes a base database system termed XooNIps that utilizes the content management system called XOOPS. XooNIps is designed for developing databases in different research fields through customization of the option menu. In a XooNIps-based database, digital resources are stored according to their respective categories, e.g., research articles, experimental data, mathematical models, stimulations, each associated with their related metadata. Several types of user authorization are supported for secure operations. In addition to the directory and keyword searches within a certain database, XooNIps searches simultaneously across other XooNIps-based databases on the Internet. Reviewing systems for user registration and for data submission are incorporated to impose quality control. Furthermore, XOOPS modules containing news, forums schedules, blogs and other information can be combined to enhance XooNIps functionality. These features provide better scalability, extensibility, and customizability to the general neuroinformatics community. The application of this system to data, models, and other information related to human pupils is described here.

Computational Biology↗

PubMed2005

Action of biologically active peptides on monkey iris sphincter and dilator muscles.

Biologically active peptides modulate pupillary responsiveness in many non-primate mammals. We examined the action of seven different peptides on iris sphincter and dilator muscles of rhesus monkey. Iris sphincter and dilator muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100Hz, 0.3 msec, 10V) was applied through a pair of platinum plate electrodes. Monkey iris sphincter and dilator muscles produced simple cholinergic and adrenergic excitatory responses respectively to electrical field stimulation. Strong field stimulation did not elicit slow Substance P (SP) mediated contractions like those in rabbit iris sphincter. Exogenously applied pituitary adenylate cyclase-activating peptide (PACAP) enhanced in a concentration-dependent manner (0.3 nM-0.1 microm) the sphincter response to field stimulation, while neuropeptide Y (NPY) and somatostatin (SRIF) attenuated it. These three peptides did not affect sphincter contractions induced by acetylcholine, and therefore were acting at presynaptically. SP, calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and galanin (GAL) had no effect (at 0.1 microm) on iris sphincter. None of seven exogenously applied peptides had an effect on monkey iris dilator muscle. The innervation of primate irises may be relatively simple compared to non-primates because each of the peptides in this study can modulate miosis or mydriasis in non-primate mammals. Future studies will be expected on the functional significance of species differences in iridial innervation.

Acetylcholine↗

PubMed2005

Prostaglandins E1 and E2, but not F2alpha or latanoprost, inhibit monkey ciliary muscle contraction.

PURPOSE: To investigate the effects of prostaglandin (PG) E1, E2, F2alpha, and latanoprost acid on the electrically evoked contractile response of isolated rhesus monkey ciliary muscle. METHODS: Longitudinal ciliary muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100 Hz, 0.3 ms, 10 V) was applied through a pair of platinum plate electrodes. RESULTS: The ciliary muscle produced atropine-sensitive excitatory contraction in response to field stimulation. PGE1 and PGE2 (1 microM) attenuated the contraction to levels that were 68% and 65.1%, respectively, of the normal amplitude. However, PGF2alpha and latanoprost acid (1 microM) did not significantly change the response amplitude. CONCLUSIONS: Our results indicate that PGF2alpha and latanoprost acid do not interact with the prostanoid receptor involved at the pre- and/or postsynaptic site. Therefore, it is unlikely that the hypotensive action by these agents is due to relaxation of the ciliary muscle.

Alprostadil↗

PubMed2005

Mutation-based genetic neural network.

Evolving gradient-learning artificial neural networks (ANNs) using an evolutionary algorithm (EA) is a popular approach to address the local optima and design problems of ANN. The typical approach is to combine the strength of backpropagation (BP) in weight learning and EA's capability of searching the architecture space. However, the BP's "gradient descent" approach requires a highly computer-intensive operation that relatively restricts the search coverage of EA by compelling it to use a small population size. To address this problem, we utilized mutation-based genetic neural network (MGNN) to replace BP by using the mutation strategy of local adaptation of evolutionary programming (EP) to effect weight learning. The MGNN's mutation enables the network to dynamically evolve its structure and adapt its weights at the same time. Moreover, MGNN's EP-based encoding scheme allows for a flexible and less restricted formulation of the fitness function and makes fitness computation fast and efficient. This makes it feasible to use larger population sizes and allows MGNN to have a relatively wide search coverage of the architecture space. MGNN implements a stopping criterion where overfitness occurrences are monitored through "sliding-windows" to avoid premature learning and overlearning. Statistical analysis of its performance to some well-known classification problems demonstrate its good generalization capability. It also reveals that locally adapting or scheduling the strategy parameters embedded in each individual network may provide a proper balance between the local and global searching capabilities of MGNN.

Algorithms↗

PubMed2004

On the asymptotic distribution of the least-squares estimators in unidentifiable models.

In order to analyze the stochastic property of multilayered perceptrons or other learning machines, we deal with simpler models and derive the asymptotic distribution of the least-squares estimators of their parameters. In the case where a model is unidentified, we show different results from traditional linear models: the well-known property of asymptotic normality never holds for the estimates of redundant parameters.

Algorithms↗

PubMed2003

Neuroscience data and tool sharing: a legal and policy framework for neuroinformatics.

The requirements for neuroinformatics to make a significant impact on neuroscience are not simply technical--the hardware, software, and protocols for collaborative research--they also include the legal and policy frameworks within which projects operate. This is not least because the creation of large collaborative scientific databases amplifies the complicated interactions between proprietary, for-profit R&D and public "open science." In this paper, we draw on experiences from the field of genomics to examine some of the likely consequences of these interactions in neuroscience. Facilitating the widespread sharing of data and tools for neuroscientific research will accelerate the development of neuroinformatics. We propose approaches to overcome the cultural and legal barriers that have slowed these developments to date. We also draw on legal strategies employed by the Free Software community, in suggesting frameworks neuroinformatics might adopt to reinforce the role of public-science databases, and propose a mechanism for identifying and allowing "open science" uses for data whilst still permitting flexible licensing for secondary commercial research.

Computational Biology↗

PubMed2003

Visiome: neuroinformatics research in vision project.

The coordinated efforts within Japan's Neuroinformatics Research in Vision (NRV) program to build a neuroinformatics portal for vision science in Japan, the 'Visiome' (Vision+Ome) Platform is presented. We introduce the general concepts underlying of the NRV Project and an example of a specific neuroinformatics study on the vertebrate retina, as developed in Visiome.

Medical Informatics↗

PubMed2003

Effect of somatostatin and galanin on isolated rabbit iris sphincter and dilator muscles.

The neuropeptides somatostatin and galanin are present in the iris and may modulate pupil diameter. We examined the effects of somatostatin and galanin on isolated rabbit iris dilator and sphincter smooth muscles that were mounted in an organ bath. An isometric transducer recorded changes in tension in response to electric field stimulation (100 Hz, 0.3 msec in duration, 10 V in strength) delivered by a pair of platinum plate electrodes. The dilator muscle response to field stimulation was not changed by either peptide, even at the highest concentrations examined. The sphincter muscle response consisted of two components: a fast component mediated by acetylcholine and slow component mediated by substance P. Both somatostatin and galanin attenuated the cholinergic component in a dose-dependent manner (from 0.3 nM to 0.1 microM) but had no effect on responses mediated by substance P. Galanin was more effective (attenuation of 43% at 0.1 microM) compared with somatostatin (attenuation of 16% at 0.1 microM) in reducing the cholinergic response. Neither peptide affected the contraction induced by acetylcholine (1mM). Therefore both peptides inhibited cholinergic transmission in the sphincter muscle, although the degree of inhibition by each was different. We conclude that somatostatin and/or galanin may induce mydriasis by attenuating cholinergic neurotransmitter release.

Acetylcholine↗

PubMed2003

Mechanical properties of the rabbit iris smooth muscles.

The study focuses on obtaining the visco-elastic properties of the iris sphincter and dilator muscles. Two kinds of experiments were performed: the isometric contraction experiment and the isotonic quick release experiment. The length-tension relationship was obtained from the former experiment. This relationship clarified the contribution of each muscle in determining the statics of the pupil. The viscous and serial elastic properties were obtained from the latter experiment. The viscosity could be expressed by the expanded Hill's equation as a function of velocity and contractile tension. We argue that serial elasticity is independent of contractile tension. These properties provide insights into the pupillary mechanism.

Animals↗

PubMed2003

A simulation analysis on mechanisms of damped oscillation in retinal rod photoreceptor cells.

The different actions of two I(h) channel blockers, zatebradine (UL-FS 49) and ZD7288, on rod photoresponses were analysed by computer simulation using a newly revised ionic current model of the rod photoreceptor, based on Hodgkin-Huxley equations. The model, adjusted to fit the experimental results of amphibian rods, shows that both of the blockers enhance the light-induced membrane hyperpolarization. Our model can also predict a mechanism of a damped oscillation arising during the recovery phase appeared only in the presence of zatebradine which, unlike ZD7288, reduces both I(h) and I(Kv). We suggest that the oscillation can appear due to the alternative activation of voltage-dependent Ca(2+) current (I(Ca)) and calcium-dependent current (I(K(Ca)) and I(Cl(Ca))) when I(Kv) is blocked, with I(K(Ca)) having a stronger effect than I(Cl(Ca)).

Action Potentials↗

PubMed2003

Neuroinformatics Research for Vision Science: NRV project.

The NRV project (Neuroinformatics Research for Vision Science) is the first project in Japan started in 1999 under the Science and Technology Agency of Japan, aimed at building the foundation of neuroinformatics research. Because of the wealth of data on the visual system, the NRV project will use vision research to promote experimental, theoretical and technical research as a pilot study on neuroinformatics. Details can be found at: http://www.neuroinformatics.gr.jp/.

Animals↗

PubMed2002

Neuroinformatics: the integration of shared databases and tools towards integrative neuroscience.

There is significant interest amongst neuroscientists in sharing neuroscience data and analytical tools. The exchange of neuroscience data and tools between groups affords the opportunity to differently re-analyze previously collected data, encourage new neuroscience interpretations and foster otherwise uninitiated collaborations, and provide a framework for the further development of theoretically based models of brain function. Data sharing will ultimately reduce experimental and analytical error. Many small Internet accessible database initiatives have been developed and specialized analytical software and modeling tools are distributed within different fields of neuroscience. However, in addition large-scale international collaborations are required which involve new mechanisms of coordination and funding. Provided sufficient government support is given to such international initiatives, sharing of neuroscience data and tools can play a pivotal role in human brain research and lead to innovations in neuroscience, informatics and treatment of brain disorders. These innovations will enable application of theoretical modeling techniques to enhance our understanding of the integrative aspects of neuroscience. This article, authored by a multinational working group on neuroinformatics established by the Organization for Economic Co-operation and Development (OECD), articulates some of the challenges and lessons learned to date in efforts to achieve international collaborative neuroscience.

Computational Biology↗

PubMed1996

A Computational Model for Color Constancy by Separating Reflectance and Illuminant Edges within a Scene.

Several psychophysical experiments have revealed that color constancy exists even in shadowed scenes where the spatial power distribution of the illuminant has abrupt step changes, while previous models for color constancy fail to distinguish shadows and reflectance changes. This article addresses this problem and proposes a computational model for color constancy which separates reflectance and illuminant edges by two modules recovering both the spatial power distribution of the illuminant and surface reflectances of an object from an input scene. Each module has a line process which interprets whether a given edge is derived from a reflectance or illuminant change based on prior knowledge of shadows: it is mainly luminance that changes at the boundry of a shadowed area. Simulation results show that the proposed model correctly detects reflectance and illuminant edges and illuminant colors, and successfully removes the illuminant from the input scene. This suggests that recovering both surface reflectance and the spatial power distribution of the illuminant is one of the possible ways to achieve color constancy in shadows. Copyright 1996 Elsevier Science Ltd.

Journal Article↗

PubMedDate not supplied

Simulation analysis of receptive-field size of retinal horizontal cells by ionic current model.

The size of the receptive field of retinal horizontal cells changes with the state of dark/light adaptation. We have used a mathematical model to determine how changes in the membrane conductance affect the receptive-field properties of horizontal cells. We first modeled the nonlinear membrane properties of horizontal cells based on ionic current mechanisms. The dissociated horizontal cell model reproduced the voltage-current (V-I) relationships for various extracellular glutamate concentrations measured in electrophysiological studies. Second, a network horizontal cell model was also described, and it reproduced the V-I relationship observed in vivo. The network model showed a bell-shaped relationship between the receptive-field size and constant glutamate concentration. The simulated results suggest that the calcium current is a candidate for the bell-shaped length constant relationship.

Animals↗