Hideki Imada

Protective Effect Against 17β-Estradiol on Neuronal Apoptosis in Hippocampus Tissue Following Transient Ischemia/Recirculation in Mongolian Gerbils via Down-Regulation of Tissue Transglutaminase Activity

We analyzed the protective effect of 17β-estradiol (17β-ED) injection against delayed neuronal death in the hippocampus tissue of the brain in Mongolian gerbils after transient ischemia/recirculation treatment, especially in relation with bcl-2 gene expression and enzymatic activity changes of caspase-3 and tissue transglutaminase (tTGase). Daily intraperitoneal injection of 17β-ED to the animal after the ischemia stimulated the expression of an apoptosis suppressor gene, bcl-2, in the hippocampal tissue for a week. The gradually increasing apoptotic enzyme activity of caspase-3 and increased number of TUNEL positive fragmented neuronal nuclei caused by ischemic attack in the gerbil brain were clearly suppressed by 17β-ED administration. The reduced activity and enzyme protein of tTGase, a neurodegenerative marker of apoptosis in the hippocampus after ischemia, were also restored to nearly normal levels by 17β-ED injection. These results suggest that daily 17β-ED administration to the gerbil after transient ischemic insult with progressing neuronal deteriorative changes in hippocampus tissue can effectively prevent apoptotic changes through a molecular cascade involving gene expression regulation.

Distribution and development of P2Y1-purinoceptors in the mouse retina

There is increasing evidence that ATP acts on purinergic receptors and mediates synaptic transmission in the retina. In a previous study, we raised the possibility that P2X-purinoceptors, presumably P2X2-purinoceptors in OFF-cholinergic amacrine cells, play a key role in the formation of OFF pathway-specific modulation. In this study, we examined whether the P2Y1-purinoceptors can function in cholinergic amacrine cells in the mouse retina since cholinergic amacrine cells in the rat retina express P2Y1-purinoceptors. P2Y1-purinoceptors were shown to be expressed in dendrites of both ON- and OFF-cholinergic amacrine cells in adults. At postnatal day 7, there was immunoreactivity for P2Y1-purinoceptors in the soma of cholinergic amacrine cells. At postnatal day 14, weak immunoreactivity for P2Y1-purinoceptors was detected in the dendrites but not in the soma of cholinergic amacrine cells. At postnatal day 21, strong immunoreactivity for P2Y1-purinoceptors was detected in dendrites of cholinergic amacrine cells. The expression pattern of P2Y1-purinoceptors was not affected by visual experience. We concluded that P2Y1-purinoceptors are not involved in the OFF-pathway-specific signal transmission in cholinergic amacrine cells of the mouse retina.

Influence of lycopene intake to changes of SOD and GPx activities on hippocampal tissue of Mongolian gerbil after cerebral ischemia/reperfusion

ior in the open-field test, passive-avoidance test, and home-cage activity test. In the screening, we isolated a behavioral mutant which exhibited a significant increase in spontaneous locomotor activity in the open-field test and home-cage activity test. We identified a missense mutation in theTuba1 gene in this mutant. This mutation results in an aspartic acid to glycine substitution TUBA1 protein. Detailed behavioral analyses revealed that heterozygote exhibited inattention to novel object and attention deficit and hyperactivity were improved by methylphenidate injection. Additionally, the results of behavioral pharmacological analysis using methylphenidate, immunohistochemical analyses, electronmicroscopy observation of the brain tissue, and BrdU labeling suggested that this mutant is a good animal model of neurodevelopmental disorders.

The distribution of T lymphocytes, B lymphocytes, and dendritic-like cells of the anal tonsil in the laboratory shrew, Suncus murinus.

We investigated the distribution of T lymphocytes, B lymphocytes, and S‐100 protein‐immunoreactive dendritic‐like in the anal tonsil of the laboratory shrew, Suncus murinus. In adult animals, T lymphocytes were located mainly at the periphery of the anal tonsil, especially around small blood vessels. B lymphocytes were located in the central and subepithelial region of the anal tonsil, which includes primary lymphoid follicles, and in which there are small numbers of scattered T lymphocytes. B and T lymphocytes were distributed over 72.7 and 27.3% of the tonsillar area, respectively. However, their areas of distribution were not clearly distinguished. The areas containing B lymphocytes were enriched in S‐100 protein antibody‐immunoreactive cells, which exhibited a dendritic shape. These S‐100‐positive cells appeared to be identical to the follicular dendritic cells (FDC) seen in the follicles of lymphoid organs. These results suggest that the anal tonsils constitute one of the gut‐associated lymphoid tissues (GALT), and that a function of the anal tonsil includes the capture of intruding antigens that would generate protective antibody responses. Microsc. Res. Tech., 2011.

Immunohistochemical and calcium-imaging analyses of histamine and histamine receptors in mammalian retinal neurons

Visual information is segregated into different features such as color, form, and motion at the level of the retina. Particularly, the direction of image motion is coded by direction-selective (DS) ganglion cells in the retina. By generating SPIG1-GFP knock-in mice to label SPIG1-positive cells, we genetically identified physiological subtypes of ON DS ganglion cells and their central pathways. We show that SPIG1positive ON DS ganglion cells code upward motion and project to the dorsal part of the medial terminal nucleus (MTN) via the inferior fasciculus of the accessory optic tract (AOT), whereas SPIG1-negative ON DS ganglion cells code downward motion and project to the ventral part of the MTN via the superior fasciculus of the AOT. The upward preferences of SPIG1-positive ON DS ganglion cells develop normally in dark-reared mice. The MTN neurons are activated by optokinetic stimuli only of the vertical motion as shown by Fos expression analysis. Our findings provide insights into how information about the direction of image motion is detected by the retina and deciphered by the brain.

Effect of lycopene as antioxidant on hippocampus of Mongolian gerbil after ischemia/reperfusion

Stroke is one of the leading cause of adult disability worldwide. Recently treatment with tissue plasminogen activator (t-PA) has been applied to acute ischemic patients that must be used during a limited time window after the stroke onset. In the present study, we found that MAP kinase phosphatase-1 (MKP-1) is induced transcriptionally in revascularized brain after focal stroke by performing differential display analysis. Although MKP-1 was not induced translationally, it was accumulated in the nucleus and co-localized with phosphorylated JNK, one of substrates for MKP-1, in primary cultured neurons and neuroblastoma N1E 115 cells under H/R condition. In brain sections of rat MCA-O reperfusion model, immunoreactivity of MKP-1 and phoshoJNK were detected in the neuronal cells in peri-ischemic penumbra. These results raise the possibility that activation of MKP-1 in combination with t-PA treatment could be a promising therapy for acute ischemic patients beyond the current 3 hours limit in the future.