Biomedical subjects

T Itano

Publications and source records attributed to T Itano.

At least 55 records · Page 3Linked to original sources

PubMed1996

A chronological study of the expression of glial fibrillary acidic protein and calbindin-D28 k by reactive astrocytes in the electrically lesioned rat brain.

Immunoreactivity of neuronal and glial marker proteins of reactive astrocytes around the electrically damaged pyramidal layer and stratum radiatum of the hippocampal CA1 region and corpus callosum was chronologically studied in electrically lesioned rat brains. A monoclonal antibody against calbindin-D28 k (CD28-Ab) and a polyclonal antibody against glial fibrillary acidic protein (GFAP-Ab) were used for immunostaining. Immunoreactivity of CD28 and GFAP in the reactive astrocytes was detected in brains 1-6 weeks post-lesion but not in non-lesioned brains. The number of immunohistochemically stained reactive astrocytes around the electrically damaged areas were counted and then compared with the number of those in the same areas of non-lesioned brains. The number of CD28- and GFAP-immunoreactive astrocytes began to increase around the lesion from 1-3 weeks following lesion in the pyramidal layer of the hippocampal CA1 region and from 1-4 weeks following lesion in the stratum radiatum of the hippocampal CA1 region and corpus callosum. These immunoreactive astrocytes could be observed for 6 weeks (the maximum survival time studies) in all areas of the lesioned brains studied. The increase in the number of reactive astrocytes might have been induced by the stimulatory effects of neurotrophic factors, or growth factors, produced around the lesioned site. The constancy in the number of reactive astrocytes after 3 and 4 weeks in the lesioned areas may have been due to the termination of the initial phase of the repair process, i.e. space-filling. Reactive astrocytes which were stained by GFAP-Ab were separated into two groups, based on the presence of CD28, i.e. CD28-positive and CD28-negative reactive astrocytes. The presence of CD28 might confer certain functions via calcium-mediated mechanisms on CD28-positive astrocytes in addition to the constructive role mediated by GFAP.

Animals↗

PubMed1996

Developmental alteration of the expression and kinase activity of cyclin-dependent kinase 5 (Cdk5)/p35nck5a in the rat retina.

Neuronal Cdc2-like kinase has been purified from the bovine brain as a proline-directed serine/threonine kinase. This kinase is a heterodimer of Cdk5 and p35nck5a and influences neuronal maturation or sprouting in the normal brain. In this study, we showed the expression of Cdk5/p35nck5a kinase in the developing rat retina. The expression of Cdk5 and p35nck5a increased between 1 week and 3 weeks after birth. These expression levels were most prominent from 2 weeks to 3 weeks after birth and decreased after 4 weeks. The developmental change of Cdk5/p35nck5a kinase activity coincided with those of the expression of p35nck5a and Cdk5. An immunohistochemical study showed that Cdk5 was expressed in the ganglion cells and in some cells in the inner nuclear layer at an early stage. With retinal development, Cdk5 was expressed in the inner plexiform layer also. In the adult, the expression of Cdk5 was restricted to the inner plexiform layer and to some cells in the inner nuclear layer. These changes of localization in the developing retina were very close to those of B-50/GAP-43. On the other hand, the expression of p35nck5a was restricted to the soma of the neuron in the developing retina. This subcellular localization in the developing retina agreed with that in the developing rat brain. The expression levels of Cdk5 and p35nck5a in retina of rats raised from fetus to 3 weeks after birth in darkness were 36% and 40% respectively, of the baseline for control rats. Moreover, the kinase activity in rats raised in darkness was lower than that in control rats. These data suggest that Cdk5/p35nck5a may play a role in neuronal plasticity in the developing rat retina.

Animals↗

PubMed1996

Enhanced expression of the protein kinase substrate annexin in human hepatocellular carcinoma.

Annexin (AX) constitutes a new family of Ca2+-dependent membrane-binding proteins; 13 of them have been described. Among these, annexin-1 (AX-I) has displayed many biological functions in vitro. Its actual role in vivo, however, remains unknown. We already reported that AX-I was expressed in proliferating (regenerating) hepatocytes at both protein and messenger RNA (mRNA) levels. The role of AX-I in human hepatocellular carcinoma (HCC) remains obscure. In this study, the amounts of AX-I at protein and mRNA levels, as well as its localization, have been determined in the normal human liver, chronic hepatitis liver, and nontumorous and tumorous portions of HCC. AX-I was rarely found in normal and chronic liver tissues, whereas it is overexpressed at both the transcriptional and translational levels in tumorous and nontumorous regions of HCC. In addition, more AX-I was expressed in the tumorous portion than the nontumorous portion of HCC. AX-I was present in the hepatocytes and HCC cells, localized mainly in the cytoplasm. AX-I was expressed in poorly differentiated cancer cells. Furthermore, AX-I was tyrosine-phosphorylated in HCC. We also found that some of the AX-I- positive hepatocytes in the nontumorous tissues were derived from a particular subset of parenchymal cells (stem or oval cells). These results indicate that AX-I plays an important role in the malignant transformation process leading to HCC and that it is closely related to the histological grade of HCC. HCC would offer a novel tool with which to study the function of AX-I in malignant transformation.

Annexin A1↗

PubMed1995

Developmental changes of cyclin dependent kinase 5 subcellular localization in the rat cerebellum.

Cyclin dependent kinase 5 (Cdk5) phosphorylates tau protein, a microtubule-associated protein, at pathological sites in vitro as well as in Alzheimer's disease brain. The enzyme is therefore regarded as an important candidate responsible for the progression of Alzheimer's disease. We and others have suggested that the enzyme has physiological roles in brain development and maturation. In this study, we investigated the exact distribution and developmental changes of the enzyme in cerebellum by immunohistochemistry and non-radioactive in situ hybridization. Immunohistochemistry demonstrated that Cdk5 was consistently expressed in the cerebellum at all developing stages. However, the subcellular localization of Cdk5 dramatically changed during maturation of the cerebellum. In the early neonatal stage, Cdk5 was strongly expressed in the cell bodies of neurones. With neuronal maturation Cdk5 immunoreactivity changed its subcellular localization from the cell body to axon. In terminally differentiated neurons, the immunoreactivity was only detected in the axon. These results suggest that subcellular localization of Cdk5 is strictly regulated and may play an important role in neuronal maturation.

Alzheimer Disease↗

PubMed1995

pp60c-src expression in rat spermatogenesis.

A fractionation of the membrane extract of rat testes revealed the existence of pp60c-src kinase activity. The expression of pp60c-src was examined in the developing rat testes. The immunecomplex kinase assay using a monoclonal antibody specific to pp60c-src (mAb327) showed that the expression of pp60c-src kinase activity increased during the development of rat testes and declined in the adult. The increase in pp60c-src kinase activity observed during the development of rat testes was accompanied with an increase in the amount of pp60c-src protein. The peak period in the increase of pp60c-src kinase activity well coincided with the timing, when the spermatogenesis by meiosis just began. The immunohistochemical staining of pp60c-src in rat testes demonstrated that pp60c-src is most abundantly expressed in the spermatids which are the spermatogenic cells in the post-meiotic phase of the spermatogenesis. These findings strongly suggest that pp60c-src is a developmentally regulated gene product which is involved in rat spermatogenesis.

Amino Acid Sequence↗

PubMed1995

Developmental alteration and neuron-specific expression of bone morphogenetic protein-6 (BMP-6) mRNA in rodent brain.

Bone morphogenetic proteins (BMPs) are a group of proteins which induce bone formation from mesenchymal cells. The existence of BMPs in the nervous system as well as in bone tissue has recently been reported. In this study, we show that BMP-6 is neuron-specific, and describe the temporal and spatial expression patterns of BMP-6 mRNA in the developing rat and gerbil brain. Northern blot analysis showed that the BMP-6 transcript level was specifically high from newborn to 3 weeks after birth compared with those in fetal and adult rats. In situ hybridization showed that most of the neurons possessed high levels of BMP-6 mRNA in the neonatal brain, while in the adult brain, BMP-6 mRNA level was significantly decreased in most of the neurons except those in hippocampus which retained high levels. Furthermore, to show that the BMP-6 expression was specific to neurons, we induced delayed neuronal cell death and compensative glial cell proliferation in the gerbil hippocampus by transient ischemia. Our findings collectively suggest that BMP-6 is neuron-specific and may play important roles in neuronal maturation and synapse formation.

Animals↗

PubMed1995

Morphological changes in the hippocampus in amygdaloid kindled mouse.

To clarify the origin and maintenance of epileptogenesis, morphological changes in the hippocampus of amygdaloid-kindled mice were analyzed at different stages of kindling. The granule cell size in dentate gyrus and the pyramidal cell size in CA1 were clearly decreased depending on seizure stage. The cell size in CA2 was increased and density in dentate gyrus and CA2 was reduced, significantly. The morphological changes in hippocampus associated with kindling must be closely related to the acquisition and the maintenance of epileptogenesis. The results support the hypothesis that seizure-induced damage of neurons may lead to formation of new synaptic connections that produce abnormal hyperexitability and result in seizures.

Amygdala↗

PubMed1995

Histochemical demonstration of heavy metals in mouse skin.

The localization of heavy metals in normal mouse skin was investigated light microscopically using the Neo-Timm staining method. Positive staining was found in the horny layer of epidermis, connective tissue of dermis and in hair roots. Chelation of heavy metals by pretreatment with diethyldithiocarbamate prevented this staining. The study demonstrates that heavy metals, mainly zinc, are localized in the mouse skin and that the Neo-Timm staining method is useful for the investigation of the role of zinc in this organ.

Animals↗

PubMed1995

Involvement of annexin-I in glucose-induced insulin secretion in rat pancreatic islets.

Annexin-I was demonstrated to specifically present in islets and not in exocrine tissues of the rat pancreas and to have a diffuse and homogeneous distribution in all islet cells in our previous study. In the present report, to clarify the functions of annexin-I in rat pancreatic islets, especially in beta-cells, we investigated the role of annexin-I in insulin secretion. Immunoelectron microscopic analysis of pancreatic beta-cells demonstrated that immunogold particles reactive to annexin-I were almost exclusively observed on most of the insulin-containing granules (approximately 90%) and less frequently located in cytosol and other organelles, such as the endoplasmic reticulum and mitochondria. The number of annexin-I gold particles located on insulin granules after oral glucose administration was significantly increased compared with that observed in fasted rats. Moreover, when the isolated islets were stimulated by a high concentration of glucose (20 mM), the phosphorylation of annexin-I was markedly enhanced, and it was synchronized to insulin secretion. This phosphorylation mainly occurred on serine residues. H-7 (100 microM), a potent inhibitor of protein kinase-C, inhibited the phosphorylation to about 90%. These findings suggest that annexin-I might be involved in the regulatory mechanism of glucose-induced insulin secretion in rat pancreatic islets via phosphorylation-dephosphorylation processes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1994

In situ localization of rat testis-specific calcineurin B subunit isoform beta 1 in the developing rat testis.

In situ localization and developmental changes in expression of testis-specific calcineurin B subunit isoform beta 1 was examined in rat testis. Two different sizes of mRNA signal, 4.0 kb and 0.9 kb, were detected by Northern blot hybridization. Both signals were expressed synchronously with the start of meiosis at 3 weeks after birth, and increased depending on the maturation of spermatogenesis. In situ hybridization using non-radioactive riboprobes showed that the beta 1 mRNA was specifically localized to spermatocytes where meiosis occurs but none or very little was observed in spermatogonia, spermatids, Sertoli or Leydig cells.

Animals↗

PubMed1994

Immunosuppressants and calcineurin inhibitors, cyclosporin A and FK506, reversibly inhibit epileptogenesis in amygdaloid kindled rat.

Calcineurin (CaN) immunoreactivity and content increased markedly in kindled rat brain, and this increment was due to CaN in the membrane fraction. Investigation of the effects of cyclosporin A and FK506 (immunosuppressants which inhibit CaN activity in T lymphocytes) in the kindling phenomena showed that the kindling stage progression was reversibly blocked by these drugs. These findings suggest that calcineurin may play an essential role in acquiring epileptogenesis in kindling.

Amygdala↗

PubMed1994

Mutual interaction between host and graft tissues in embryonic neural transplantation.

The differentiation of AChE-positive cells in embryonic neural grafts from various brain regions into the hippocampus after fimbria-fornix transection was investigated. Rat fetal cell suspensions of basal forebrain, hippocampus, mesencephalon or cortex were prepared from fetuses of either embryonic day 14 (E14) or day 19 (E19) gestational age, and these were transplanted into the rat brain after unilateral fimbria-fornix transection. Dense acetylcholinesterase (AChE) positive fibres were observed in both E14 and E19 basal forebrain grafts. These fibres were also found in E14 hippocampal grafts. However E19 hippocampal grafts did not have any AChE-positive fibres. These results suggest that E14 hippocampal grafts might be affected by the host brain tissues and differentiate into cholinergic neurones.

Acetylcholinesterase↗

PubMed1994

Ipsilateral motor control of the forelimb in the congenitally acallosal mouse.

The corticospinal projections of mice with callosal agenesis were investigated using electro-physiological and horseradish peroxidase techniques. In the normal mouse, intracortical stimulation of the motor area with the microelectrode resulted in contralateral contraction of the forelimb, whereas ipsilateral contraction was observed in the acallosal mouse. Hence, mice with congenital absence of the corpus callosum show physiologically ipsilateral motor control. Furthermore, latency of the forelimb contraction elicited by electrical stimulation of the acallosal mouse was slightly shorter than that of the normal mouse. On the other hand, it was confirmed by a horseradish peroxidase technique that the corticospinal tract and peripheral motor neurons in the spinal cord of the acallosal mouse were identical to those of the normal mouse.

Agenesis of Corpus Callosum↗

PubMed1994

Changes in annexin I and II levels during the postnatal development of rat pancreatic islets.

The expression patterns and the dynamic changes in content of both annexin I and annexin II in the rat pancreatic islets during postnatal development were investigated by both western blot analysis and immunohistochemistry. Immunohistochemical methods clearly demonstrated the presence of annexins I and II exclusively in pancreatic islets, while exocrine tissues were not stained by anti-annexin antibodies. Pancreatic islets were diffusely stained with no specific differences in distribution between different cell types. The expression of annexin I in pancreatic islets gradually increased with postnatal development. A developmental study of annexins I and II by western blot analysis essentially supported the results obtained by immunohistochemistry. In addition, the increasing expression of two protein tyrosine kinases, epidermal growth factor-receptor/kinase and pp60src, which phosphorylate annexin I and annexin II, respectively, and of protein kinase C, which phosphorylates both proteins, was also shown during postnatal development in rat pancreatic islets. Thus, a relationship between the expression of annexins I and II and the maturation of islet cell function is suggested.

Actins↗

PubMed1994

Involvement of annexin I and annexin II in hepatocyte proliferation: can annexins I and II be markers for proliferative hepatocytes?

Annexin is the name of a new family of Ca(2+)-dependent membrane-binding proteins. Eleven types of its related proteins have been reported to date. Among those, annexin I and annexin II have been reported to possess many biological functions in vitro. Its actual role in vivo, however, is yet unknown. The involvement of annexin I and annexin II in the proliferation processes of hepatocytes was examined in the following aspects: (a) hepatocyte proliferation after carbon tetrachloride-induced liver damage, (b) hepatocyte regeneration after partial hepatectomy and (c) postnatal development of hepatocytes. These results showed collectively that annexin I and annexin II were increased in proliferative (or regenerative) hepatocytes, suggesting that both proteins play a certain role in the proliferation event. Furthermore, annexin I- and annexin II-positive hepatocytes always show a wider distribution than that of proliferating cell nuclear antigen or cytokeratin 7-positive hepatocytes, indicating that annexin I and annexin II may be useful markers for detecting not only actively proliferating hepatocytes but also hepatocytes in preproliferative and postproliferative stages.

Animals↗

PubMed1993

Effect of ceruletide on epileptogenesis in amygdaloid kindled rats.

The inhibitory effects of ceruletide (CLT), a cholecystokinin-8 (CCK)-like peptide, were investigated in the epileptogenesis in the amygdaloid kindled rats. Lower doses of CLT (20-80 micrograms/kg) inhibited the progression of kindling process. After acquiring C5 stage, a higher dose (160 micrograms/kg) was required to suppress the seizure susceptibility. These results, in light of several previous studies showing no serious side effects, suggest that CLT might be useful as an anti-epileptogenic agent for clinical usage.

Amygdala↗

PubMed1993

Ceruletide suppresses rotational behavior in lesioned rats via CCKA receptors.

The effects and pharmacological mechanisms underlying the inhibiting effect of ceruletide, a cholecystokinin (CCK)-related peptide, on apomorphine-induced turning behavior in 6-hydroxydopamine lesioned rats were investigated. For this purpose, selective CCKA and CCKB receptor antagonists were used. Ceruletide (50-400 micrograms/kg, s.c.) dose dependently suppressed apomorphine-induced rotational behavior. The antiapomorphine effect of ceruletide was reversed by the selective CCKA receptor antagonist, devazepide, but not by the selective CCKB receptor antagonist, L-365,260. This suggests that the suppression ceruletide exerts on hyperactive nigrostriatal dopamine neurons is mediated by CCKA receptors.

Animals↗

PubMed1993

Effect of embryonic hippocampal transplantation in amygdaloid kindled rat.

Embryonic neural tissue was transplanted into previously kindled rats. A thirteen- to fourteen-day embryonic hippocampal cell suspension was grafted in the stratum oriens near the CA2 area of the hippocampus. Almost 80% of the animals had a good recovery and became seizure-free. Injection of neocortical cells or saline did not show any positive effect on the kindling susceptibility. Although 20 day embryonic cell transplantation was also effective, the effect did not last as long as the 13- to 14-day embryonic transplantation. These observations open the possibility that the neural grafts may be used for therapy of medically intractable epilepsies.

Amygdala↗