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Biomedical subjects

H Kiyama

Publications and source records attributed to H Kiyama.

At least 37 records · Page 2Linked to original sources
PubMed2000

Nerve growth factor protects oligodendrocytes from tumor necrosis factor-alpha-induced injury through Akt-mediated signaling mechanisms.

Tumor necrosis factor-alpha is thought to be one of the most important inflammatory cytokines associated with the demyelinating disease multiple sclerosis. We determined whether neurotrophins could protect oligodendrocytes from tumor necrosis factor-alpha-mediated cytotoxicity. Among the neurotrophins tested, nerve growth factor was most effective at preventing cell death. Nerve growth factor also prevented the tumor necrosis factor-induced loss of mitochondrial membrane potential. Overexpression of constitutively active Akt, a downstream target of phosphatidylinositol 3-kinase, but not of constitutively active MEK, protected oligodendrocytes from tumor necrosis factor-induced injury. Moreover, overexpression of dominant-negative Akt negated the protective effects of nerve growth factor on tumor necrosis factor-mediated oligodendrocyte cytotoxicity. These findings indicate that the Akt pathway is crucial in nerve growth factor-mediated oligodendrocyte protection.

Androstadienes↗
PubMed2000

GAP-43 N-terminal translocation signal targets beta-galactosidase to developing axons in a pan-neuronal transgenic mouse line.

Tracing neural connectivity is important in understanding the intricacy of the nervous system as this represents the functional unit throughout the system. Here, we provide evidence that beta-galactosidase (beta-gal) linked to the N-terminal axonal translocation signal of GAP-43 provides a reproducible and versatile reporter system for analyzing the developing nervous system in vivo. When expressed by the GAP-43 promoter in transgenic mice, the fusion protein is detected equally within the developing axons of the peripheral and the central nervous systems, directly reflecting the promoter activity.

Animals↗
PubMed2000

Akt/protein kinase B prevents injury-induced motoneuron death and accelerates axonal regeneration.

Motoneurons require neurotrophic factors for their survival and axonal projection during development, as well as nerve regeneration. By using the axotomy-induced neuronal death paradigm and adenovirus-mediated gene transfer, we attempted to gain insight into the functional significances of major growth factor receptor downstream cascades, Ras-extracellular signal-regulated kinase (Ras-ERK) pathway and phosphatidylinositol-3 kinase-Akt (PI3K-Akt) pathway. After neonatal hypoglossal nerve transection, the constitutively active Akt-overexpressing neurons could survive as well as those overexpressing Bcl-2, whereas the constitutively active ERK kinase (MEK)-overexpressing ones failed to survive. A dominant negative Akt experiment demonstrated that inhibition of Akt pathway hastened axotomy-induced neuronal death in the neonate. In addition, the dominant active Akt-overexpressing adult hypoglossal neurons showed accelerated axonal regeneration after axotomy. These results suggest that Akt plays dual roles in motoneuronal survival and nerve regeneration in vivo and that PI3K-Akt pathway is probably more vital in neuronal survival after injury than Ras-ERK pathway.

Animals↗
PubMed2000

Damage-induced neuronal endopeptidase (DINE) is a unique metallopeptidase expressed in response to neuronal damage and activates superoxide scavengers.

We isolated a membrane-bound metallopeptidase, DINE (damage-induced neuronal endopeptidase), by differential display PCR using rat normal and axotomized hypoglossal nuclei. The most marked properties of DINE were neuron-specific expression and a striking response to axonal injury in both the central nervous system and peripheral nervous system. For instance, cranial and spinal nerve transection, ischemia, corpus callosum transection, and colchicine treatment increased DINE mRNA expression in the injured neurons, whereas kainate-induced hyperexcitation, immobilization, and osmotic stress failed to up-regulate DINE mRNA. Expression of DINE in COS cells partially inhibited C2-ceramide-induced apoptosis, probably because of the activation of antioxidant enzymes such as Cu/Zn-superoxide dismutase, Mn-superoxide dismutase, and glutathione peroxidase through the proteolytic activity of DINE. These data provide insight into the mechanism of how injured neurons protect themselves against neuronal death.

Animals↗
PubMed2000

Safety and efficacy of blood donation prior to elective cardiac surgery in anemic patients.

OBJECTIVE: To determine the safety and effectiveness of blood donation in anemic patients, we harvested blood from cardiac patients with baseline hemoglobin levels below 11.0 g/dl. METHODS: Subjects were 118 patients who underwent elective cardiac surgery between January 1994 and October 1997. We assigned patients to 1 of 2 groups based on their entry hemoglobin level: an anemic group (hemoglobin < 11.0 g/dl, n = 20) and a nonanemic group (hemoglobin > or = 11.0 g/dl, n = 98). All patients received subcutaneous administration of recombinant human erythropoietin, and autologous blood was collected once a week for at least 3 weeks before the scheduled surgery date if the hemoglobin level exceeded 10.5 g/dl. RESULTS: No statistically significant differences were seen between the 2 groups in patient profiles or surgical data. The estimated hemoglobin increase did not differ significantly between groups at any time point. The total collected blood volume per patient was greater in the nonanemic group than in the anemic group (1098 +/- 224 ml vs. 712 +/- 334 ml), but the difference in volume was not statistically significant. The percentage of patients who received allogeneic blood did not differ significantly between groups. No side effects were associated with hemoglobin level prior to donation because the incidence of side effects was similar across hemoglobin levels. CONCLUSIONS: This study suggests that autologous blood donation reduces the need for allogeneic blood in patients with baseline hemoglobin levels below 11.0 g/dl.

Aged↗
PubMed2000

Endothelin-converting enzymes and endothelin receptor B messenger RNAs are expressed in different neural cell species and these messenger RNAs are coordinately induced in neurons and astrocytes respectively following nerve injury.

There is some evidence that endothelins may be a signal mediator between neuronal and glial cells, at least in some regions of the brain. To evaluate this possibility, the localization of messenger RNAs for endothelin-converting enzymes and endothelin receptor B in the rat brain were examined using in situ hybridization histochemistry. The messenger RNAs for endothelin-converting enzyme-1 and endothelin-converting enzyme-2 were expressed mainly in neurons located in various brain regions, whereas the messenger RNA for endothelin receptor B was mainly localized in the astrocytes located throughout the brainstem, Bergmann glia, choroid plexus and ependymal cells. The localization patterns of endothelin-converting enzyme and endothelin receptor B messenger RNAs were strikingly different. For instance, in the cerebellum, endothelin-converting enzyme-1 messenger RNA was localized in Purkinje cells, and endothelin-converting enzyme-2 mRNA was expressed in Purkinje cells and granule cells. On the other hand, endothelin receptor B messenger RNA was expressed in Bergmann glia and the astrocytes located in the granule cell layer. This suggests that final cleavages of big endothelins are performed on neuronal cells, and the major target of the processed endothelins could be astrocytes, which express endothelin receptor B most abundantly in the brain. Since evidence that endothelin is implicated in brain injury has also accumulated, we examined whether the expressions of endothelin-converting enzymes and endothelin receptor B are regulated by nerve injury. Following hypoglossal nerve injury, expression of messenger RNA for endothelin-converting enzymes-1 and -2 and endothelin receptor B was enhanced in the injured motor neurons and astrocytes respectively. The up-regulation of these messenger RNAs was also confirmed by a reverse transcription-polymerase chain reaction based strategyThese results lead us to suggest that endothelin can be an inducible intercellular mediator between injured neurons and astrocytes in response to nerve injury.

Animals↗
PubMed2000

Morphological changes and expression of protein kinase CK2 beta subunit in the microglia after hypoglossal nerve transection.

Following hypoglossal nerve transection, the microglia of the rat hypoglossal nucleus expressed protein kinase CK2 beta subunit immunoreactivity. CK2 beta immunostaining occurred on the operated side from postoperative day 3; on day 5 we observed strong immunoreactivity and the immunopositive microglial cell processes surrounded the injured neurones. Thereafter, the immunoreactivity decreased gradually and on day 10 the immunopositive cells surrounded only a few injured neurones. Electron microscopic observations on the hypoglossal nucleus revealed microglia-neuronal contact within 3 hours of nerve injury, and by day 3 all the injured neurones were in contact with microglial cells. These observations indicated that microglia-neuronal contact occurred earlier than the CK2 beta subunit immunoreactivity. CK2 may not be implicated during the initial migration of the microglia to the injured neurones; however, it may enhance the growth and elongation of the microglial cell processes around the injured neurones.

Animals↗
PubMed2000

Mutant loricrin is not crosslinked into the cornified cell envelope but is translocated into the nucleus in loricrin keratoderma.

Loricrin is a major constituent of the epidermal cornified cell envelope. We have recently identified heterozygous loricrin gene mutations in two dominantly inherited skin diseases, the ichthyotic variant of Vohwinkel syndrome and progressive symmetric erythrokeratoderma, collectively termed loricrin keratoderma. In order to see whether the mutant loricrin molecules predicted by DNA sequencing are expressed in vivo and to define their pathologic effects, we raised antibodies against synthetic peptides corresponding to the mutated sequences of loricrin. Immunoblotting of horny cell extracts from loricrin keratoderma patients showed specific bands for mutant loricrin. Immunohistochemistry of loricrin keratoderma skin biopsies showed positive immunoreactivity to the mutant loricrin antibodies in the nuclei of differentiated epidermal keratinocytes. The immunostaining was localized to the nucleoli of the lower granular cell layer. As keratinocyte differentiation progressed the immunoreactivity moved gradually into the nucleoplasm leaving nucleoli mostly nonimmunoreactive. No substantial staining was observed along the cornified cell envelope. This study confirmed that mutant loricrin was expressed in the loricrin keratoderma skin. Mutant loricrin, as a dominant negative disrupter, is not likely to affect cornified cell envelope crosslinking directly, but seems to interfere with nuclear/nucleolar functions of differentiating keratinocytes. In addition, detection of the mutant loricrin in scraped horny layer could provide a simple noninvasive screening test for loricrin keratoderma. J Invest Dermatol 115:1088-1094 2000

Cell Nucleolus↗
PubMed2000

Identification of a novel WD repeat-containing gene predominantly expressed in developing and regenerating neurons.

In the present study, we have identified a novel gene, NDRP (for neuronal differentiation-related protein), which is predominantly expressed in developing and regenerating neurons. The predicted NDRP comprises 1,019 amino acid residues and has 6 WD repeats in the N-terminal half and multiple potential nuclear localization signals (NLSs) at the C-terminal part. This molecule shows no significant structural similarity with any other molecules in available databases. In situ hybridization and immunohistochemistry revealed the highest expression of NRDP in sensory neurons, for instance, olfactory epithelia and neural layer of retina during embryonic development, as well as in perinatal dorsal root ganglions. The expression of this gene in intact motor neurons such as in the hypoglossal nerve was undetectable but became obvious after axotomy. These results suggest that the product of this gene might be involved in the development of sensory neurons as well as the regeneration of motor neurons.

Amino Acid Sequence↗
PubMed2000

[Three-channeled aortic dissection: selection of surgery based on the images].

Three patients with 3-channeled dissection were operated upon. Images of the dissection were enlargement of the false lumens, compression of the true lumen by enlarged false lumens and visceral arteries of false lumen origin. These prevent the use of cardiopulmonary bypass (CPB) and cause malperfusion of the viscera. Three-channeled dissecion is easy to rupture for its peculiar anatomy and total repair of the thoraco-abdominal aorta is mandatory. Fenestration brings functional recovery of malperfused viscera and enables the patients to be placed on CPB for total repair. Two patients underwent infrarenal and descending aorta fenestration followed by the total repair of thoraco-abdominal aorta successfully. A third patient has been placed on the strict CT follow-up following the infrarenal fenestration.

Adult↗
PubMed2000

Injury-specific expression of activating transcription factor-3 in retinal ganglion cells and its colocalized expression with phosphorylated c-Jun.

PURPOSE: To ascribe activating transcription factor (ATF)-3 as a specifically induced transcription factor after ON injury and to describe its putative role as a modulator of c-Jun transactivation. METHODS: The adult rat optic nerve was crushed intraorbitally, and expression profiles of ATF-3, ATF-2, and phosphorylated c-Jun (p-c-Jun) were examined by immunohistochemistry and ISH. Western blot analysis for ATF-3 and -2 were also performed. Furthermore, colocalized detection of c-Jun mRNA with ATF-2 or -3 was attempted with a combined method of simultaneous immunohistochemistry and in situ hybridization. RESULTS: In response to optic nerve injury, substantial expression of ATF-3 as well as that of p-c-Jun was observed in the retinal ganglion cells, whereas no expression of ATF-3 was seen in other noninjured retinal cells. In contrast, ATF-2 was normally expressed abundantly in both retinal ganglion cells and displaced amacrine cells, but expression dropped in retinal ganglion cells after nerve injury. The expression profiles of ATF-2 and -3 after optic nerve injury were confirmed by Western blot analysis. A higher degree of colocalization was observed for ATF-3 and c-Jun than the modest codetection for ATF-2 and c-Jun. CONCLUSIONS: The transcription factor ATF-3 is specifically induced upon optic nerve injury and colocalizes with p-c-Jun in surviving ganglion cells. These findings suggest that both ATF-3 and c-Jun are crucial to trigger various transcriptional responses and may act synergistically during the survival phase of the optic nerve in the injury model.

Activating Transcription Factor 2↗
PubMed1999

Discordant expression of c-Ret and glial cell line-derived neurotrophic factor receptor alpha-1 mRNAs in response to motor nerve injury in neonate rats.

Adult motoneurons can survive following axotomy, whereas neonate motoneurons result in cell death. Following hypoglossal nerve axotomy in neonate rat, Glial cell line-Derived Neurotrophic Factor (GDNF) receptor alpha-1 (GFRalpha-1) mRNA expression was dramatically suppressed in the injured motoneurons, while a slight increase of c-Ret mRNA expression was observed. In adult, both GFRalpha-1 and c-Ret mRNAs increased substantially after axotomy. The present result suggests that the difference of motoneuron fate after axotomy may be partly due to the coordinate or discordant responses of GFRalpha-1 and c-Ret expression to nerve injury.

Aging↗
PubMed1999

A novel mammalian T-box-containing gene, Tbr2, expressed in mouse developing brain.

We have identified and characterized a new member of the mammalian brain-specific T-box gene family, Tbr2, which is closely related to mouse Tbr1, and to the Xenopus earliest mesodermal gene, Eomesodermin. As Tbr1, Tbr2 is predominantly expressed in some regions of the developing brain, but in a strikingly complementary manner. On embryonic day 14.5 (E14.5), Tbr2 mRNA expression was observed in the mesencephalon and rhombencephalon in contrast to Tbr1 which was expressed mostly in the telencephalon. At this stage, Tbr2 mRNA was readily detectable in the postmitotic and differentiating neurons located in various brain regions, i.e., oculomotor, red, trigeminal, vestibular, facial, and hypoglossal nuclei. However, expression of Tbr2 in these nuclei became undetectable on E18.5. In contrast, Tbr2 mRNA expression was detected in the hippocampus only from E18.5 onwards. Whereas Tbr2 expression disappeared in most parts of the mature adult brain, it remained detectable in the hippocampus and olfactory bulb, regions where some neuronal precursors retain their differentiation potential. These results suggest that Tbr2 may play a crucial role in differentiating neurons rather than in proliferating or already differentiated neurons. In addition, similarly to Xenopus Eomesodermin, mouse Tbr2 showed biphasic expression; a first peak around E6.5 and a second peak around E14.5, suggesting that Tbr2 may also be important at early stages of gastrulation.

Amino Acid Sequence↗
PubMed1999

IPP isomerase, an enzyme of mevalonate pathway, is preferentially expressed in postnatal cortical neurons and induced after nerve transection.

To understand the molecular mechanisms underlying the developmental processes of the cerebral cortex, we screened genes whose mRNA expression was up-regulated in neonatal in the rat cortex to a greater extent than in adult by differential display and obtained five genes. Among these genes, we focused on pyrophosphate (isopentenyl diphosphate, dimethylallyl diphosphate: IPP) isomerase gene, the product of which is known as an enzyme of the mevalonate pathway. Rat IPP isomerase was recently cloned and the gene expression was shown to be dependent on the activation of the mevalonate pathway. Its expression and roles in the brain, however, have not been investigated hitherto. In the present study, Northern blots and in situ hybridization analysis showed that at embryonic stage weak signals for IPP mRNA were diffusely detected in the CNS, and the signal in the cortex became intense at postnatal day 1 and maximized in almost all neurons of all layers at postnatal day 7 with a subsequent reduction. At 8 weeks, the expression of IPP isomerase mRNA in neurons decreased, while it was detected in the oligodendrocytes in the regions containing abundant nerve fibers. These findings suggested that IPP isomerase contributes to postnatal neuronal maturation and myelination. We also demonstrated that IPP isomerase mRNA is induced after nerve axotomy, which suggests a relationship between neuronal regeneration and IPP isomerase. Taken together, these results suggest that elevation of IPP isomerase mRNA levels in neurons contributes to construction of nerve fibers both during the postnatal period in the cortex and their regeneration.

Animals↗
PubMed1999

Expression of gicerin, a novel cell adhesion molecule, is upregulated in the astrocytes after hypoglossal nerve injury in rats.

Gicerin is an integral membrane glycoprotein which mediates cell-cell and cell-extracellular matrix (ECM) interactions in the nervous system. We studied gicerin expression in the hypoglossal nucleus post transection using in situ hybridization and immunocytochemistry. We found that hypoglossal nerve injury resulted in a significant increase in gicerin expression. Its expression levels reached peak values in reactive astrocytes surrounding axotomized motoneurons of the ipsilateral hypoglossal nucleus 14 days after hypoglossal nerve injury. The results indicate that gicerin is up-regulated during nerve regeneration, suggesting that gicerin expressed in the reactive astrocytes might be involved in the processes of nerve regeneration.

Animals↗
PubMed1999

Expressed-sequence-tag approach to identify differentially expressed genes following peripheral nerve axotomy.

Gene expression profiles in the rat hypoglossal nucleus after axotomy were demonstrated using expressed-sequence-tag (EST) approach. To demonstrate the gene-expression profiles after axotomy, nerve-transected hypoglossal nuclei were dissected and collected from about 1000 rats, with which a cDNA library was constructed. More than 750 clones were sub-cloned and sequenced from the library. The clones which hit frequently are likely to be associated with mitochondrial respiratory chain, cytoskeletal protein and protein synthesis. One hundred three clones from among the sequenced clones were further processed for histological screening using unilateral-hypoglossal nerve-transected brain sections by in situ hybridization histochemistry. In situ hybridization study revealed that 26% of clones examined showed upregulated expression of mRNA in response to axotomy. They included genes encoding proteins associated with glucose, lipid and protein metabolism, cytoskeleton, neurotransmission and immune reaction. The present EST analysis may have an advantage in targeting genes which are associated with nerve injury with a good efficacy, as compared with other methods such as differential display and subtraction.

Animals↗
PubMed1999

Nitric oxide in the flocculus works the inhibitory neural circuits after unilateral labyrinthectomy.

We previously reported that nitric oxide (NO) production in the unipolar brush (UB) cells is involved in vestibular compensation [T. Kitahara, N. Takeda, P.C. Emson, T. Kubo, H. Kiyama, Changes in nitric oxide synthase-like immunoreactivities in unipolar brush cells in the rat cerebellar flocculus after unilateral labyrinthectomy, Brain Res. 765 (1997) 1-6]. To further elucidate the role of NO-mediated signaling in flocculus after unilateral labyrinthectomy (UL), we examined UL-induced Fos expression, a marker of neural activity, in vestibular brainstem with continuous floccular infusions of Nomega-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO synthase (NOS). After UL with floccular l-NAME infusions, Fos expression appeared in bilateral medial vestibular (MVe) and prepositus hypoglossal (PrH) nuclei. After UL with floccular saline infusions, however, Fos expression was observed only in the ipsi-MVe and contra-PrH. Furthermore, it has been revealed that UL with l-NAME infusions caused more severe vestibulo-ocular disturbances than UL with saline infusions at the initial stage [Kitahara et al. Brain Res. 765 (1997) 1-6]. Therefore, it is suggested that UL with floccular l-NAME infusions activates the contra-MVe and ipsi-PrH neurons and causes more severe imbalance between intervestibular nuclear activities at the initial stage. NO-mediated signaling in flocculus could be a possible driving force of the flocculus-mediated inhibition on the contra-MVe and ipsi-PrH at the initial stage of vestibular compensation.

Animals↗