Biomedical subjects

Yoshiro Inoue

Publications and source records attributed to Yoshiro Inoue.

12 recordsLinked to original sources

PubMed2006

Developmental localization of potassium chloride co-transporter 2 (KCC2) in the Purkinje cells of embryonic mouse cerebellum.

Developmental shift in GABA actions from depolarization to hyperpolarization occurs as a result of decreasing the intracellular Cl(-) concentration regulated by K(+)-Cl(-) co-transporter 2 (KCC2). To clarify the time-course of the developmental shift on the Purkinje cells, we examined KCC2-localization in the embryonic mouse cerebellum. The KCC2 was first detected within the Purkinje cells in the Purkinje cell layer of the hemisphere at embryonic day 15 (E15) and the vermis at E17, but the ventricular and intermediate zones were negative. These results suggest that GABA might become inhibitory on the Purkinje cells after their settling in the Purkinje cell layer.

Age Factors↗

PubMed2005

Developmental expression of GABA transporter-1 and 3 during formation of the GABAergic synapses in the mouse cerebellar cortex.

In the brain, gamma-amino butyric acid (GABA), released extrasynaptically and synaptically from GABAergic neurons, plays important roles in morphogenesis, expression of higher functions and so on. In the GABAergic transmission system, plasma membrane GABA transporters (GATs) mediate GABA-uptake from the synaptic cleft in the mature brain and are thought to mediate diacrine of cytosolic GABA in the immature brain. In the present study, we focused on two GATs (GAT-1 and GAT-3) in the mouse cerebellar cortex, which are widely localized in neural and glial cells. Firstly, we examined the localization of GATs in the dendrites and cell bodies of developing GABAergic neurons, where GABA is extrasynaptically distributed, to clarify the GABA-diacrine before synaptogenesis. Secondly, we examined the developmental changes in the localization of GATs to reveal the development of the GABA-uptake system. Neither transporter was detected within the dendrites and cell bodies of GABAergic neurons, including Purkinje, stellate, basket and Golgi cells, in the immature cerebellar cortex. GAT-1 was observed within the Golgi cell axon terminals after postnatal day 5 (P5) and presynaptic axons of stellate and basket cells after P7. GAT-3 was localized within the astrocyte processes, sealing the GABAergic synapses in the Purkinje cell and granular layers after P10. These results indicated that GABA-diacrine did not work in the mouse cerebellar cortex. The onset of GAT-1-expression was prior to that of GAT-3. GAT-1 started to be localized within the GABAergic axon terminals during synapse formation. GAT-3 started to be localized within astrocyte processes when they sealed the synapses.

Age Factors↗

PubMed2004

Morphological development and maturation of the GABAergic synapses in the mouse cerebellar granular layer.

In the adult central nervous system (CNS), gamma-amino butyric acid (GABA) is a predominant inhibitory neurotransmitter, which regulates glutamatergic activity. Recent studies have revealed that GABA serves as an excitatory transmitter in the immature CNS, and is involved in brain morphogenesis. To elucidate how GABA exerts its effect on immature neurons and how GABAergic synapses are formed, we examined both development of pre- and post-synaptic elements of the GABAergic synapses formed between granule and Golgi cells in the mouse cerebellar granular layer. Immunohistochemistry for glutamic acid decarboxylase (GAD) demonstrated that GABA was localized throughout the Golgi cells before postnatal day 7 (P7), and became confined to the axon terminals during the second postnatal week. Electron microscopic analysis demonstrated that GABAergic synapses were clearly detected at P10. In situ hybridization and immunohistochemistry for the GABA(A) receptor alpha1 and alpha6 subunits, which are mainly involved in inhibitory synaptic transmission, demonstrated that both subunits appeared at P7. Distribution of both subunits expanded in the granular layer with special reference to the development of GABAergic synapses. Furthermore, the majority of the subunits accumulated adjacent to the GABAergic terminals. These results suggested that in the granular layer, GABA might be non-synaptically secreted from Golgi cell axons and dendrites during the first postnatal week. From the second postnatal week, GABA is synaptically released and begins to mediate inhibitory transmission. Furthermore, it was suggested that GABAergic innervation could initiate expression and trafficking of the GABA(A) receptors containing the alpha1 and alpha6 subunits.

Animals↗

PubMed2004

Transient expression of GABAA receptor alpha2 and alpha3 subunits in differentiating cerebellar neurons.

In the adult mammalian brain, synaptic transmission mediated by gamma-amino butyric acid (GABA) plays a role in inhibition of excitatory synaptic transmission. During brain development, GABA is involved in brain morphogenesis. To clarify how GABA exerts its effect on immature neurons, we examined the expression of the GABAA receptor alpha2 and alpha3 subunits, which are abundantly expressed before alpha1 and alpha6 subunits appear, in the developing mouse cerebellum using in situ hybridization. Proliferating neuronal precursors in the ventricular zone and external granular layer expressed neither alpha2 nor alpha3 subunits. Hybridization signals for the alpha2 and alpha3 subunit mRNAs first appeared in the differentiating zone at embryonic day 13 (E13). The alpha2 subunit was detected in the migrating and differentiating granule cells and cerebellar nucleus neurons until postnatal day 14 (P14). Hybridization signals for the alpha3 subunit mRNA, on the other hand, were localized in the developing Purkinje cells and cerebellar nucleus neurons, and disappeared from Purkinje cells by the end of first postnatal week. Taken together, this indicated that the alpha2 and alpha3 subunits were abundantly expressed in distinct types of cerebellar neurons after completing cell proliferation while forming the neural network. These results suggest that GABA might extrasynaptically activate the GABAA receptors containing alpha2 and/or alpha3 subunits on the differentiating neurons before finishing the formation of synapses and networks, and could be involved in neuronal differentiation and maturation in the cerebellum.

Animals↗

PubMed2004

Tetraspanin protein CD9 is a novel paranodal component regulating paranodal junctional formation.

The axoglial paranodal junction is essential for the proper localization of ion channels around the node of Ranvier. The integrity of this junction is important for nerve conduction. Although recent studies have made significant progress in understanding the molecular composition of the paranodal junction, it is not known how these membrane components are distributed to the appropriate sites and interact with each other. Here we show that CD9, a member of the tetraspanin family, is present at the paranode. CD9 is concentrated in the paranode as myelination proceeds, but CD9 clusters become diffuse, associated with disruption of the paranode, in cerebroside sulfotransferase-deficient mice. Immunohistochemical and Western blot analysis showed that CD9 is distributed predominantly in the PNS. Ablation of CD9 in mutant mice disrupts junctional attachment at the paranode and alters the paranodal components contactin-associated protein (also known as Paranodin) and neurofascin 155, although the frequency of such abnormalities varies among individuals and individual axons even in the same mouse. Electron micrographs demonstrated that compact myelin sheaths were also affected in the PNS. Therefore, CD9 is a myelin protein important for the formation of paranodal junctions. CD9 also plays a role in the formation of compact myelin in the PNS.

Animals↗

PubMed2004

Extrasynaptic localization of GABA in the developing mouse cerebellum.

In the adult brain, gamma-amino butyric acid (GABA) is synaptically released and mediates inhibitory transmission. Recent studies have revealed that GABA is a trophic factor for brain development. To reveal the distribution of GABA and its secretion mechanisms during brain development, we investigated the immunohistochemical localization of two molecules, GABA and vesicular GABA transporter (VGAT), which is a GABAergic vesicle protein, in the developing mouse cerebellum by means of newly developed antibodies. Furthermore, we tested the relationship between developmental changes in distribution of above two molecules in the presynapses and ontogeny of GABAergic synapses. GABAergic synapses were detected by immunohistochemistry for the GABA(A) receptor alpha1 subunit, which is an essential subunit for inhibitory synaptic transmission in the mature cerebellar cortex. Until postnatal day 7 (P7), GABA was localized throughout the GABAergic neurons, and VGAT accumulated at axon varicosities and growth cones, where the alpha1 subunit did not accumulate. After P10, both GABA and VGAT became confined to the terminal sites where the alpha1 subunit was localized. These results suggested that GABA was extrasynaptically released from axon varicosities and growth cones by vesicular secretion 'exocytosis' and from all parts of GABAergic neurons during the cerebellar development by non-vesicular secretion 'diacrine'.

Amino Acid Transport Systems↗

PubMed2004

GABAergic signaling in the developing cerebellum.

In the adult central nervous system (CNS), GABA is a predominant inhibitory neurotransmitter that regulates glutamatergic activity. Recent studies have revealed that GABA serves as an excitatory transmitter in the immature CNS and acts as a trophic factor for brain development. Furthermore, synaptic transmission by GABA is also involved in the expression of higher brain functions, such as memory, learning and anxiety. These results indicate that GABA plays various roles in the expression of brain functions and GABAergic roles change developmentally in accordance with alterations in GABAergic transmission and signaling. We have investigated morphologically the developmental changes in the GABAergic transmission system and the key factors important for the formation of GABAergic synapses and networks using the mouse cerebellum, which provides an ideal system for the investigation of brain development. Here, we focus on GABA and GABA(A) receptors in the developing cerebellum and address the processes of how GABA exerts its effect on developing neurons and the mechanisms underlying the formation of functional GABAergic synapses.

Animals↗

PubMed2003

Normal formation of the postsynaptic elements of GABAergic synapses in the reeler cerebellum.

Synaptic transmission mediated by gamma-amino butyric acid (GABA) plays an important role in inhibition of glutamatergic excitatory transmission and expression of higher brain functions, such as memory, learning and anxiety. To elucidate mechanisms underlying formation of the postsynaptic elements for GABAergic transmission, we employed the reeler mutant mice in this study. In the reeler cerebellum, abnormal cytoarchitecture and an aberrant environment affect the formation of neural networks and maturation of neurons. We examined the expression and localization of GABA(A) receptor alpha subunits in the reeler cerebellum and determined whether various abnormalities in the reeler mice affected formation of the postsynaptic elements. In situ hybridization analysis revealed that the specific expression of alpha subunit mRNAs in each neuronal type was preserved. Abnormal expression of alpha subunits was not detected, although GABAergic networks were altered and neuronal maturation was severely disturbed. Immunohistochemistry for the alpha1 and alpha6 subunits, which were expressed abundantly in the reeler cerebellum, revealed that both subunit proteins accumulated at positions adjacent to GABAergic terminals. These results, taken together, suggested that expression of the GABA(A) receptor subunits in postsynaptic neurons might be genetically determined, but trafficking and accumulation of the subunit proteins at the GABAergic synapse may be induced by GABAergic innervation.

Animals↗

PubMed2002

Distal extension of climbing fiber territory and multiple innervation caused by aberrant wiring to adjacent spiny branchlets in cerebellar Purkinje cells lacking glutamate receptor delta 2.

Organized synapse formation on to Purkinje cell (PC) dendrites by parallel fibers (PFs) and climbing fibers (CFs) is crucial for cerebellar function. In PCs lacking glutamate receptor delta2 (GluRdelta2), PF synapses are reduced in number, numerous free spines emerge, and multiple CF innervation persists to adulthood. In the present study, we conducted anterograde and immunohistochemical labelings to investigate how CFs innervate PC dendrites under weakened synaptogenesis by PFs. In the GluRdelta2 knock-out mouse, CFs were distributed in the molecular layer more closely to the pial surface compared with the wild-type mouse. Serial electron microscopy demonstrated that CFs in the knock-out mouse innervated all spines protruding from proximal dendrites of PCs, as did those in the wild-type mouse. In the knock-out mouse, however, CF innervation extended distally to spiny branchlets, where nearly half of the spines were free of innervation in contrast to complete synapse formation by PFs in the wild-type mouse. Furthermore, from the end point of innervation, CFs aberrantly jumped to form ectopic synapses on adjacent spiny branchlets, whose proximal portions were often innervated by different CFs. Without GluRdelta2, CFs are thus able to expand their territory along and beyond dendritic trees of the target PC, resulting in persistent surplus CFs by innervating the distal dendritic segment. We conclude that GluRdelta2 is essential to restrict CF innervation to the proximal dendritic segment, by which territorized innervation by PFs and CFs is properly structured and the formation of excess CF wiring to adjacent PCs is suppressed.

Animals↗

PubMed2002

Vav3 is regulated during the cell cycle and effects cell division.

Vav3 is a member of the family of guanine nucleotide exchange factors implicated in the regulation of Rho GTPases. Although the exact in vivo function of Vav3 is unknown, evidence from several studies indicates a role distinct from Vav2 or Vav1. Here we report that the expression of Vav3 is regulated during the cell cycle. Strikingly, Vav3 was transiently up-regulated in HeLa cells during mitosis, whereas enforced expression of Vav3 perturbed cytokinesis and led to the appearance of multinucleated cells. These effects of Vav3 were RhoA-dependent, required phosphorylation of the regulatory tyrosine 173, but were not enhanced by N-terminal truncations. Thus, this report establishes that expression of Vav3 is strictly regulated in a cell cycle-dependent manner and implicates Vav3 in the control of cytokinesis.

Alkaline Phosphatase↗

PubMed2002

Development of astrocytes in the lamina cribrosa sclerae of the mouse optic nerve, with special reference to myelin formation.

In the mouse optic nerve, the optic nerve fiber layer in the retina, the optic papilla and the lamina cribrosa sclerae (LCS) just after penetrating the eyeball failed to generate myelin, whereas the optic nerve proper in the orbit was occupied by myelinated nerve fibers. The present study investigated development of the architecture of LCS, where the axons develop from unmyelinated to myelinated type, to elucidate how the initial part of axons was unmyelinated. At the LCS of the adult optic nerve, well developed astrocytes densely formed a cytoplasmic mesh-like frame through which unmyelinated fibers passed. The astrocytes here contained numerous and densely packed intermediate glial filaments and cell organelles. This framework formed by astrocytes appeared to be completed between 7 and 14 postnatal days before oligodendrocyte progenitors, migrated from the chiasm side, reached the proximal end of LCS, and began myelin formation. Thus the failure in myelin formation at the intraocular part and LCS possibly depended upon unsuccessful migration of oligodendrocytes beyond LCS constructed by specialized astrocytes, although other inhibitory factors for myelin formation, such as adhesion molecules distributed around LCS, may be unsolved.

Animals↗

PubMedDate not supplied

Prospective endoscopic follow-up results of reconstructed gastric tube.

BACKGROUND/AIMS: Recent advances in the treatment of esophageal cancer have afforded better prognosis for patients. Despite the increased need to monitor the progress of patients with reconstructed digestive tracts over the long-term, no reliable prospective studies have yet been conducted. This prospective study determined secondary disease of the reconstructed gastric tube after esophagectomy for esophageal cancer. METHODOLOGY: One hundred and fourteen patients who underwent esophagectomy and reconstructed gastric tube via the posterior mediastinal route between April 1992 and March 1999 at Akita University Hospital, were followed up. Follow-up endoscopy was carried out once a year to determine the incidence and characteristics of secondary disease of the reconstructed gastric tube. RESULTS: Fifty-four (47%) patients were found to have secondary gastric abnormalities. Of these, 4 patients (3.5%) had carcinoma of the gastric tube, 12 patients (10.5%) had benign gastric tumor, 7 patients (6.1%) had gastric ulcers, and 40 patients (35.1%) had erosive or hemorrhagic gastritis. Three patients found to have early gastric cancer upon periodic follow-up endoscopy underwent successful complete resections. CONCLUSIONS: Annual follow-up endoscopy is vital to the detection of early, curative secondary gastric cancer and ulceration in patients following esophagectomy for esophageal cancer.

Aged↗