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Dive into the research topics where Kozo Sugioka is active.

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Featured researches published by Kozo Sugioka.


Journal of Neurochemistry | 2002

Docosahexaenoic acid provides protection from impairment of learning ability in Alzheimer's disease model rats

Michio Hashimoto; Shahdat Hossain; Toshio Shimada; Kozo Sugioka; Hiroshi Yamasaki; Yoshimi Fujii; Yutaka Ishibashi; Jun-Ichiro Oka; Osamu Shido

Docosahexaenoic acid (C22:6, n‐3), a major n‐3 fatty acid of the brain, has been implicated in restoration and enhancement of memory‐related functions. Because Alzheimers disease impairs memory, and infusion of amyloid‐β (Aβ) peptide (1–40) into the rat cerebral ventricle reduces learning ability, we investigated the effect of dietary pre‐administration of docosahexaenoic acid on avoidance learning ability in Aβ peptide‐produced Alzheimers disease model rats. After a mini‐osmotic pump filled with Aβ peptide or vehicle was implanted in docosahexaenoic acid‐fed and control rats, they were subjected to an active avoidance task in a shuttle avoidance system apparatus. Pre‐administration of docosahexaenoic acid had a profoundly beneficial effect on the decline in avoidance learning ability in the Alzheimers disease model rats, associated with an increase in the cortico‐hippocampal docosahexaenoic acid/arachidonic acid molar ratio, and a decrease in neuronal apoptotic products. Docosahexaenoic acid pre‐administration furthermore increased cortico‐hippocampal reduced glutathione levels and glutathione reductase activity, and suppressed the increase in lipid peroxide and reactive oxygen species levels in the cerebral cortex and hippocampus of the Alzheimers disease model rats, suggesting an increase in antioxidative defence. Docosahexaenoic acid is thus a possible prophylactic means for preventing the learning deficiencies of Alzheimers disease.


Clinical and Experimental Pharmacology and Physiology | 2004

Improvement of spatial cognition with dietary docosahexaenoic acid is associated with an increase in Fos expression in rat CA1 hippocampus

Yoko Tanabe; Michio Hashimoto; Kozo Sugioka; Megumi Maruyama; Yoshimi Fujii; Rika Hagiwara; Toshiko Hara; Shahdat Hossain; Osamu Shido

1. Twenty 5‐week‐old male Wistar rats were divided into two groups: one group was fed a fish oil‐deficient diet and the other group was fed the same diet supplemented with per orally administered docosahexaenoic acid (DHA) for 12 weeks.


Congenital Anomalies | 1992

A Developmental Study of Reflex and Activity in Rats with Microcephaly Induced by Prenatal Methylazoxymethanol Acetate (MAM) Treatment

Kozo Sugioka; Takashi Yamadori

Pregnant Wistar rats were given a single i. p. injection of 30 mg/kg methylazoxymethanol (MAM) acetate or saline on day 13 of pregnancy (vaginal plug = day 0). All offspring were subjected to reflex tests during the preweaning period (surface righting reflex, from 3 to 12 days of age; negative geotaxis reflex, from 5 to 12 days of age), and then selected male rats were subjected to open‐field test during the postweaning period (from 21 to 35 days of age). The MAM‐treated rats showed significantly longer latencies in the both reflex tests, and also significant hyperactivity in the open‐field test. These behavioral alterations were analyzed in relation to the large size reduction in the cerebral cortex and the morphological abnormalities of the hippocampus in the MAM‐treated rats.


Developmental Brain Research | 1996

Retrograde fluorescent double-labeling study of bilaterally projecting retinal ganglion cells in albino rats at different stages of development

Kai Dong; A.K.M. Farid Ahmed; Tingyu Qu; Kozo Sugioka; Koshi Yamada; Takashi Yamadori

Injection of the fluorescent tracers 10% Evans blue (EB) and 4% fluoro-gold (FG) into the right and the left dorsal lateral geniculate nucleus, respectively, of albino rats at different stages of development demonstrated the presence of double-labeled retinal ganglion cells that projected bilaterally into both the dorsal lateral geniculate nuclei (dLGN). Findings confirmed that the distribution of these double-labeled cells was gradually reduced after birth, being confined to the peripheral temporoventral quarter (temporal-ventral crescent) of the retina after postnatal day 15. We estimated the proportion of double-labeled cells to total labeled cells in the same area at different stages of development (0-90 days); values ranged from 35.3% in the neonate to 5.27% in the adult rat which suggests that the majority of double-labeled cells and/or their axons were lost early in development. That a small number of ganglion cells were observed to project bilaterally in the adult rats suggested that these cells conduct the same visual information to both hemispheres throughout the animals life.


Journal of The Autonomic Nervous System | 1994

Cerebral ischemia alters glucose transporter kinetics across rat brain microvascular endothelium. Quantitative analysis by an in situ brain perfusion method.

Hisahiko Suzuki; Tatsuya Nagashima; Katsuzo Fujita; Norihiko Tamaki; Kozo Sugioka; Takashi Yamadori; Michio Yamaguchi

The purpose of this study was to quantify the changes of blood-brain barrier glucose transporter kinetics following cerebral ischemia using an in situ brain perfusion technique. Sixty-four adult male Sprague-Dawley rats were divided into control and ischemia groups, and a four-vessel occlusion model was used to provide an ischemic insult. To obtain regional capillary permeability area products of glucose and regional perfusion fluid flow rates, the perfusion fluid was dually labeled with 2-deoxy[14C]glucose and [3H]diazepam, and the brain was perfused at a constant rate via the external carotid artery. After sampling tissues from the brain, dual scintillation counting was performed and both regional perfusion fluid flow rates and regional capillary permeability area products were calculated. We determined kinetic parameters, including Vmax, Km and Kd as described in the Michaelis-Menten equation, by the non-linear least squares method. In the ischemia group, a decrease in Vmax and an increase in Km were recognized, which mean decreases in the affinity and the number of functioning glucose transporters. These results suggest that cerebral ischemia downregulates the blood-brain barrier glucose transporters.


Brain & Development | 1980

Ultrastructural study on myelination in rat spinal cord during the early postnatal stage.

Takafumi Yoshioka; Kenichirou Inomata; Kozo Sugioka; Kazushige Nakamura

The progress of myelination and the appearance of myelinated fibers in the anterior funiculus of the lumbar spinal cord of newborn rats were examined by electron microscopy. Myelin was seen only in the relatively larger axons on the first postnatal day, and the number of myelinated axons increased in number with age, but no tract-specific development in myelination could be observed in the anterior funiculus. During the early development of the white matter in the spinal cord, active immature oligodendrocytes, whose cytological characteristics differed from those of mature oligodendrocytes, were seen. The cytoplasmic processes of these immature oligodendrocytes possessed electron dense material, which might be contributive to oligodendrocytic phagocytosis. This element might play a significant role in the myelination mechanism.


Brain Research | 1995

Bifurcated projections of retinal ganglion cells bilaterally innervate the lateral geniculate nuclei in the cat

Kai Dong; Tingyu Qu; A.K.M. Farid Ahmed; Tomiyoshi Setsu; Kozo Sugioka; Takashi Yamadori

Cats were injected with the fluorescent retrograde tracers, Fluoro-Gold (FG) and Evans Blue (EB), into the left and right lateral geniculate nuclei (LGN), respectively. About 4.56% of the ganglion cells in the temporal retina were double-labeled by these dyes. 4.7% of these cells were of the large type, 30.3% were of the medium type, and 65% were classified as cells of the small type. These results indicate that members of all three ganglion cell size classes, mainly those of small type, bilaterally innervate the LGN via axonal bifurcation.


Neuroscience Research | 1998

Spatial memory impairment in experimentally-induced microencephalic rats correlates with the morphological abnormality in the hippocampus

Kozo Sugioka; Tomiyoshi Setsu; Toshio Terashima

The ability of spatial recognition in microencephalic rats under a radial-arm maze task was examined. These rats were obtained from Jcl: Wistar rats treated with a single dose of 25 mgikg methylazoxymethanol acetate I(MAM) on the day 13 of pregnancy (vaginal plug = day 0). At stage 1, the MAM-treated rats as well as control rats were trained to run to obtain a reward at the end of each of a radial-arm maze for 20 sessions. At stage 2, a delayed radial-arm maze task was administered to these 2 groups to examine the retention of working memory. In this task, 5, 10, 20 and 30 min of delay intervals were introduced immediately after the first free 4 choices and then the rats were tested to obtain the remaining 4 rewards. ‘The MAM rats showed significantly more errors than the control rats in the first 8 choices (stage I). The retention test revealed that the MAM-treated rats showed an impairment of working memory when the retention interval was IO min or more (stage 2). These behavioral results shown in the MAM-treated rats were considered to be due to the effects of MAM on the hippocampus (occasional disruptions of the CA 1 pyramidal layer and/or numerous ectopic cell mass), probably but not to its effects on the neocortex (less brain weight or marked decrease in cortical thickness).


Neuroscience Research | 1996

2019 Bifurcated projections of several structures in the forebrain to the bilateral lateral habenular nuclei in the wistar albino rat

Tingyu Qu; Kai Dong; Kozo Sugioka; Takashi Yamadori

Sensory cells in the vomeronasal epithelium are replaced following experimentally induced degeneration. Unilateral section of the vomeronasal nerves in hamster results in degeneration of sensory cells followed by replacement of the sensory cell population. A quantitative analysis was made to determine the time course and degree of cell replacement in the vomeronasal epithelium following unilateral transaction of the vomeronasal nerves. Histological measurements of the number of sensory cells and epithelial thickness were made for up to 60 days postoperatively. Measurements from the experimental side were expressed as a percentage of tbe contralateral control side. There was gradual degeneration of sensory cells, the number decreasing to 50% by day 2 and 16 % by day 6. During days 7-15 cell replacement was observed. Cell number increased significantly and reached a level of 118% of control by day 15. At long recovering times (40-60 days) & number was restored to 96 % of control. Epithelial thickness decreased to 60-70 % during the degeneration period (day 4-7) and did not return to control levels. After 40-60 days of recovery epithelial thickness was at 70% of control. This study confirms that vomeronasal sensory cells are capable of replacement following degeneration. However, epithelial thickness did not return to control levels. Findings suggest that the total number of replacement cells was not limited by the reduced thickness of the epithelium and that recovery mechanisms may function to restore an optimum cell number.


Neuroscience Research | 1996

2334 A ¦14C¦ 2-deoxy-D-glucose study of the hippocampal subfields related to shuttlebox avoidance learning in the rat. The third report

Kozo Sugioka; Tomiyoshi Setsu; Takashiy Amadori

In a taste-aversion learning of the pond snail Lymnaea stagnalis, an appetitive conditioned stimulus cannot induce a conditioned response for a longtime. To clarify the neuronal mechanism of this learning, we examined the synaptic connection between the NlM cell (an interneuron in central pattern generator for the feeding response) and the cerebral giant cell (CGC, a regulatory neuron to the NlM cell). IPSP in the NlM cell of the conditioned snail evoked by activation of the CGC lasted longer than that in the control snail, while there was no difference in the CGC between the conditioned and the control snail in electrophysiological properties.

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