Biomedical subjects

Satoru Kato

Publications and source records attributed to Satoru Kato.

5 recordsLinked to original sources

PubMed2005

Polymer waveguide module for visible wavelength division multiplexing plastic optical fiber communication.

We report a polymer waveguide module that provides bidirectional communication over a single plastic optical fiber (POF) with dual visible wavelength LEDs. The module is constructed using light-induced self-written waveguides, which enables a three-dimensional optical circuit for visible wavelength division multiplexing to be fabricated by an extremely simple process. We demonstrated 250 Mbits/s communication using a pair of these modules that each contained one green (lambda = 495 nm) and one red (lambda = 650 nm) LEDs by measuring the bit error rates. The results indicate that the system could transmit over more than 20 m of POF in full duplex mode.

Journal Article↗

PubMed2004

Role of purpurin as a retinol-binding protein in goldfish retina during the early stage of optic nerve regeneration: its priming action on neurite outgrowth.

Unlike mammals, the fish optic nerve can regenerate after injury. So far, many growth or trophic factors have been shown as an axon-regenerating molecule. However, it is totally unknown what substance regulates or triggers the activity of these factors on axonal elongation. Therefore, we constructed a goldfish retina cDNA library prepared from the retina treated with optic nerve transection 5 d previously, when it was just before regrowing optic axons after injury. A cDNA clone for goldfish purpurin for which expression was upregulated during the early stage of optic nerve regeneration was isolated from the retina cDNA library. Purpurin was discovered as a secretory retinol-binding protein in developing chicken retinas. Levels of purpurin mRNA and protein transiently increased and rapidly decreased 2-5 d and 10 d after axotomy, respectively. Purpurin mRNA was localized to the photoreceptor cells, whereas the protein was diffusely found in all of the retinal layers. A recombinant purpurin alone did not affect any change of neurite outgrowth in explant culture of the control retina, whereas a concomitant addition of the recombinant purpurin and retinol first induced a drastic enhancement of neurite outgrowth. Furthermore, the action of retinol-bound purpurin was effective only in the control (untreated) retinas but not in those primed (treated) with a previous optic nerve transection. Thus, purpurin with retinol is the first candidate molecule of priming neurite outgrowth in the early stage of optic nerve regeneration in fish.

Amino Acid Sequence↗

PubMed2004

A computer image processing system for quantification of zebrafish behavior.

The tropical zebrafish (Danio rerio) has frequently been used for investigating developmental biology. Here, we developed a computer image processing system for quantifying zebrafish behavior. We could acquire an image of zebrafish freely moving in an aquarium using a CCD camera through a graphic I/O board. To acquire the image of moving zebrafish in real time, we required high spatial (256 x 256 pixels) and temporal (10 frames/s) resolution. Such a high speed of data analysis was accomplished using a skipping search method. By using a small aquarium, trackings of newborn zebrafish could be traced. The velocity of adult zebrafish (7.2 cm/s) was far faster than that of newborn zebrafish (1.8 cm/s). Furthermore, by separation of occluded images of two fish, we could acquire images of the two zebrafish. They behaved as in a school in which one fish chased the other. The chasing was defined by the distance, angle and approach of the two fishes. The chasing ratio of pairs of zebrafish was 37%, whereas those of pairs of different fish were significantly reduced to less than 20%. The present image processing system is a very useful tool for quantitatively scoring the schooling behavior of multiple fish.

Animals↗

PubMed2004

Axonal regeneration of fish optic nerve after injury.

Since Sperry's work in the 1950s, it has been known that the central nervous system (CNS) neurons of lower vertebrates such as fish and amphibians can regenerate after axotomy, whereas the CNS neurons of mammals become apoptotic after axotomy. The goldfish optic nerve (ON) is one of the most studied animal models of CNS regeneration. Morphological changes in the goldfish retina and tectum after ON transection were first researched in the 1970s-1980s. Many biochemical studies of neurite outgrowth-promoting substances were then carried out in the 1980s-1990s. Many factors have been reported to be active substances that show increased levels during fish ON regeneration, as shown by using various protein chemistry techniques. However, there are very few molecular cloning techniques for studying ON regeneration after injury. In this review article, we summarize the neurite outgrowth-promoting factors reported by other researchers and describe our strategies for searching for ON regenerating molecules using a differential hybridization technique in the goldfish visual system. The process of goldfish ON regeneration after injury is very long. It takes about half a year from the start of axonal regrowth to complete restoration of vision. The process has been classified into three stages: early, middle and late. We screened for genes with increased expression during regeneration using axotomized goldfish retinal and tectal cDNA libraries and obtained stage-specific cDNA clones that were upregulated in the retina and tectum. We further discuss functional roles of these molecules in the regeneration processes of goldfish ON.

Animals↗

PubMed2003

A dissociation of gamma-butyrolactone-induced absence seizure and CRE- and AP-1 DNA-binding activities in the developing rat brain.

Generalized absence epilepsy is a neurological childhood disorder which is characterized by behavioral arrest with staring and by 3 Hz spike and wave discharges (SWDs) in the electroencephalogram (EEG). In the present study, we investigated the correlation between behavioral and EEG changes and nuclear cAMP-responsive element (CRE)- and activator protein-1 (AP-1) DNA-binding activities during gamma-butyrolactone (GBL)-induced absence seizure in the developing rat brain. In the adult postnatal day 60 (P60) rat brain, both the transcription factor activation and absence seizure in behavior and EEG were simultaneously induced 15 min after GBL injection. In the infant P20 rat or young P40 rat, a higher sensitivity to GBL induced absence epilepsy in behavior and EEG 10-15 min after injection compared with that of adult rat. By contrast, no significant increase of CRE- and AP-1 DNA-binding activities could be seen in the infant thalamus. A significant increase in CRE- and AP-1 DNA-binding activities first occurred in the P30-40 young thalamus at 30 and 90 min, respectively, after GBL injection. Such a dissociation of high inducibility of behavior and EEG changes and low inducibility of CRE- and AP-1 DNA-binding activities in the infant or young rat clearly indicates that the activation of nuclear CRE- and AP-1 DNA-binding activities is a late occurring phenomenon with a different developmental maturation of thalamocortical circuit compared with absence seizure.

4-Butyrolactone↗