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I Tooyama

Publications and source records attributed to I Tooyama.

At least 55 records · Page 3Linked to original sources
PubMed1997

Detection of C-type natriuretic peptide (CNP) and atrial natriuretic peptide (ANP-B) receptor mRNAs in rat inner ear.

C-Type natriuretic peptide (CNP) is the third member of the natriuretic peptide family which plays an important role in body fluid homeostasis. To determine a possible role of CNP in regulation of an inner ear fluid, we investigated the expression of CNP and atrial natriuretic peptide B receptor (ANP-B receptor) mRNAs in rat inner ear using a reverse transcription polymerase chain reaction (RT-PCR) method. Amplification products with sizes expected for CNP and ANP-B were detected in the inner ear. After cloning and analysis, the sequences for PCR products were identical to those of CNP or ANP-B receptor in the brain. These results indicate that both CNP and ANP-B receptor are expressed in the inner ear of the rat and suggest that CNP may play a role in inner ear function (such as regulation of inner ear fluid) in an autocrine and/or paracrine manner.

Animals↗
PubMed1997

In vivo hypoxia-induced neuronal damage with an enhancement of neuronal nitric oxide synthase immunoreactivity in hippocampus.

Although it is well known that brain ischemia is dominantly caused by hypoxia and hypoglycemia, it is still unclear how hypoxia participates in ischemia. We studied the changes in neuronal nitric oxide synthase (nNOS) and the effect of the NOS inhibitor NG-nitro-L-arginine (NNA) on hypoxia. In vivo hypoxia (5% O2/95% N2 for 30 min) induced mild degenerative neuronal changes (shrunken and eosinophilic somata with picnotic nuclei) in neurons of the CA3, the hilus of the dentate gyrus (DG) and the DG, but not in the CA1. At 3 and 7 days after hypoxia, levels of nNOS protein were significantly enhanced to 153 and 209%, but iNOS protein could not be detected. The numbers of nNOS-immunopositive neurons were significantly enhanced to 145 and 191% in the CA3, 145 and 178% in the hilus of the DG, and 243 and 387% in the DG after 3 and 7 days, respectively. In contrast, no statistical difference was determined in the CA1. We further examined the effect of NNA administered at 5 min and 3, 6, and 24 h after hypoxia. Administration of NNA (0.1 and 1 mg/kg, i.p.) significantly decreased the number of damaged neurons in the hilus of the DG and the DG. However, higher doses of NNA (10 mg/kg, i.p.) did not prevent damage. These results suggest that hypoxia alone induces enhancement of nNOS protein and nNOS immunoreactivity in neurons of the hippocampus and that NNA has biphasic effects against hypoxia-induced neuronal damage in the hilus of the DG and the DG.

Animals↗
PubMed1997

In vivo hypoxia-induced neuronal damage in dentate gyrus of rat hippocampus: changes in NMDA receptors and the effect of MK-801.

Hypoxia is a major cause of ischaemia-induced neuronal damage. In the present study, we examined the effects of in vivo hypoxia on N-methyl-D-aspartate receptors (NMDAR) in the rat hippocampus. This model of in vivo hypoxia involved placing rats in a hypoxic chamber containing 5% O2 and 95% N2 for 30 min. In the hippocampus, neuronal cells in the CA3, the hilus of the dentate gyrus and the dentate gyrus (DG) were damaged. In the CA1, which is known to be vulnerable to ischaemic damage, neuronal cells did not show hypoxia-induced damage. In vivo hypoxia-induced damage caused morphological changes in neuronal cells, such as shrunken, spindle or triangular shapes accompanied by pyknotic nuclei, but did not induce the loss of neuronal cells. On the other hand, the number of binding sites for [3H]-1-[1-(2-thienyl)cyclohexyl]-3,4-piperidine hydrochloride (TCP) gradually decreased on and after 7 days, and then maximally decreased by 25% at 21 days after hypoxia. The number of NMDAR1-immunopositive cells was decreased by 22% in the DG, but was unchanged in the CA3. Furthermore, we examined the effect of a non-competitive NMDA antagonist, (+)-5-methyl-10, 11-dihydro-5H-dibenzo[a,b] cyclohepten-5,10-imine hydrogen maleate (MK-801), on against in vivo hypoxia. The administration of MK-801 (3 mg/kg, i.p.), 30 min before hypoxia treatment, partly protected against neuronal damage in the DG, but not in the CA3. These results suggest that hypoxia-induced neuronal damage in the DG involves, in part, the activation of NMDAR.

Animals↗
PubMed1997

Protein expression of fibroblast growth factor receptor-1 in keratinocytes during wound healing in rat skin.

Fibroblast growth factors have been shown to play important roles in wound healing. To define their sites of action, we examined the expression of fibroblast growth factor receptor-1 (FGFR-1) during burn wound healing in rat skin by immunohistochemistry and western blot analysis. In cryostat sections of intact skin, little or no staining was observed. After a burn, however, staining for FGFR-1 was found in newly forming epidermis. The suprabasal layer of such epidermis, composed mostly of regenerating keratinocytes, was stained intensely, whereas keratinocytes in newly forming hair follicles were devoid of staining. Staining gradually decreased week by week after wound closure and was hardly visible 10 weeks after the burn, when the thickness of the epidermis had returned to the normal level. Staining was also found in small blood vessels and capillaries of granulation tissues of the dermis. Western blot analysis using the same antiserum was performed in the newly forming epidermis 10 d after the burn. A single band was detected with an apparent molecular weight of 120 kDa, corresponding to the short membrane-bound form of rat FGFR-1. Our study indicates that FGFR-1 is expressed during wound healing, mainly in regenerating epidermis and to some extent in blood vessels of the dermis. Fibroblast growth factors may affect the proliferation and differentiation of epidermal keratinocytes as well as angiogenesis in the dermis via the FGFR-1 expressed during wound healing.

Animals↗
PubMed1997

aFGF, endogenous satiety substance, facilitates learning, memory and immune function in aging.

aFGF injection s.c. once a week into SAMP8 was begun at 3 weeks after birth and continued for 10 months. Saline was injected as a control. learning and memory and cellular immunological functions in the aFGF group were enhanced significantly, while those of the saline group deteriorated. 1. The number of cholinergic neurons was decreased by less than 20% and ChAT activity in individual neurons in the medial septum which send monosyonaptic terminals to the hippocampus was significantly decreased in the saline group, but not so much in the aFGF group. 2. The respective densities of muscarinic and aFGF receptors, on the hippocampal neurons were significantly higher in the aFGF group than in the saline group. 3. The LTP in hippocampal slice preparations was significantly facilitated in the aFGF group, but not in the saline group. 4. The DTH, (T cell immune response) measured at the end of the 2nd and 7th months were reduced in the 7th month as compared with the 2nd month in the saline group, but aFGF group protected against this reduction. 5. These results show that aFGF provides protection against impairment of not only learning and memory but also the DTH immunoreactivity in SAMP8.

Aging↗
PubMed1996

Protection against impairment of memory and immunoreactivity in senescence-accelerated mice by acidic fibroblast growth factor.

Subcutaneous injection of aFGF once a week into senescence-accelerated mice (SAM)P8 was begun at 3 weeks after birth and continued for 10 months. Saline was injected as a control. Learning and memory and cellular immunological functions in the aFGF group were enhanced significantly, while those of the saline group deteriorated. 1. The number of cholinergic neurons was decreased by less than 20% and choline acetyltransferase activity in individual neurons in the medical septum which send monosynaptic terminals to the hippocampus was significantly decreased in the saline group, but not so much in the aFGF group. 2. The respective densities of muscarinic and NMDA receptors and the aFGF receptor, i.e., FGFR-1 on the hippocampal neurons were also significantly higher in the aFGF group than in the saline group. 3. The long-term potentiation in the hippocampal slice preparations after a brief tetanic stimulation at the Schaffer collateral/commissural afferents was significantly facilitated in the aFGF group, but not in the saline group. 4. These data indicate the normalization caused by aFGF of the medial septohippocampal circuit, which is necessary for learning and memory. 5. The delayed type hypersensitivity reactions (DTH) in the footpad caused by challenge with trinitrophenyl or sheep red blood cells as measured at the end of the 2nd and 7th months, indicated the T cell immune response. Both types of DTHs were reduced in the 7th month as compared with the 2nd month in the saline group, but the aFGF group was protected against this reduction in accordance with age. 6. These results show that aFGF provides protection against impairment of not only learning and memory but also DTH immunoreactivity in SAMP8. They also indicate a close relationship between learning and memory and T cell immune function.

Aging↗
PubMed1996

Insulin receptor mRNA in the substantia nigra in Parkinson's disease.

Neurotrophic effects resulting from the insulin/insulin receptor system have been recognized as important in determining the etiological basis of neurodegenerative disorders. In Parkinson's disease, selective neuronal loss in the substantia nigra is accompanied by decreased immunoreactivity of the insulin receptor as determined using immunohistochemical studies. We performed semiquantitative mRNA analysis by reverse transcription-polymerase chain reaction (RT-PCR) using specific primers for human insulin receptor exon 22, which encodes a region of the beta subunit of the receptor serving as a tyrosine kinase domain. The relative levels of mRNA in the substantia nigra from Parkinson's brain tissues showed a marked depression compared with those of normal controls. Further investigations are needed to decide whether this is a primary, disease-specific alteration of gene expression or merely a secondary process.

Aged↗
PubMed1996

In vivo induction of inducible nitric oxide synthase by microinjection with interferon-gamma and lipopolysaccharide in rat hippocampus.

To clarify whether the inducible nitric oxide synthase (iNOS) protein can be induced in in vivo brain, we examined the influence of direct intrahippocampal injection with interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS) in the rat. In the area surrounding the microinjection site, NOS activity (NO2- accumulation) was enhanced 24 h after injection with IFN-gamma plus LPS. Although the level of 160-kDa nNOS protein was not changed, the 130-kDa iNOS protein was induced 12 h after the injection. On the other hand, iNOS mRNA could be detected at 6 and 12 h but not at 24 h. iNOS immunoreactivity was observed in CD11b-immunopositive microglia in close proximity to the injection site, but the immunoreactivity was not colocalized with glial fibrillary acidic protein-immunopositive astrocytes. Although CD11b-immunopositive microglia were of the ramified type even after injection with vehicle after 24 h, injection with IFN-gamma plus LPS caused numerous microglia to change to the ameboid type and to express major histocompatibility complex (MHC) class II antigens. In some of these ameboidal microglia, iNOS immunoreactivity was observed. These results suggest that intrahippocampal injection with IFN-gamma plus LPS induced iNOS mRNA after 6 h and iNOS protein after 12 h in some of the ameboidal microglia that expressed MHC class II antigens in in vivo rat brain.

Animals↗
PubMed1996

Fibroblast growth factor receptor-1 in the lateral hypothalamic area regulates food intake.

Previous studies have shown that acidic and basic fibroblast growth fa ctor (aFGF and bFGF) and certain fragments of the aFGF N-terminal suppress food intake in rats due to their inhibitory actions on the glucose-sensitive neurons in the lateral hypothalamic area (LHA). The present study was planned to determine the role of FGF receptor-1 (FGFR-1), which was found in the LHA neurons of rats, on feeding regulation. The structure-activity relationship of aFGF fragments in feeding suppression was also investigated. An injection of anti-FGFR-1 antibody (250 and 350 ng) into the bilateral LHA significantly increased food intake. Synthesized aFGF fragments were infused into the III ventricle to elucidate the structure-activity relationship on the inhibition of feeding. Although aFGF-(1-29) did not affect food intake, [Ser16]aFGF-(1-29) (400 ng) and [Glu16]aFGF-(1-29) (400 NG), in which the cysteine residue at position 16 of aFGF(1-29) was replaced with structurally similar serine and glutamic acid, were observed to significantly inhibit food intake. These findings suggest that endogenous FGFR-1 in the LHA plays an important role in FGF-induced feeding suppression, while, in addition, the dissolving disulfide bond formation in aFGF fragments enhances their inhibitory effects on feeding.

Amino Acid Sequence↗
PubMed1996

Immunohistochemical demonstration of GABAB receptors in the rat gastrointestinal tract.

Immunohistochemical localization of GABA(B)-receptors was demonstrated in the rat gastrointestinal tract using a monoclonal antibody (GB-1) raised against the purified GABA(B)-receptor. Immunoreactive staining for GABA(B)-receptors was found in some populations of endocrine, muscular and neuronal components in the stomach and gut wall. Positive mucosal epithelial, probably endocrine, cells were distributed throughout the stomach and intestine. Double immunostaining indicated that such positive cells for GABA(B)-receptors often co-possessed serotonin in the small intestine but not in the gastric body. In the muscular layer of the digestive canal, positive staining was seen as dotty granules punctuated on the surface of muscle fibers. In the enteric nervous system, positive neuronal somata were found in both submucosal and myenteric ganglia throughout the entire canal extending from the stomach to the rectum. This is the first report to visualize the cellular localization of GABA(B)-receptors in the gastrointestinal system of the rat, and should provide a fundamental basis for future studies on gastrointestinal functions regulated by GABA(B)-receptors.

Animals↗
PubMed1995

Neuroprotective effects of NBQX on hypoxia-induced neuronal damage in rat hippocampus.

Models of cerebral ischaemia were used for analysis of mechanism of neuronal cell death and/or damage. Ischaemia is caused dominantly by severe hypoxia and hypoglycaemia: in the present study, we examined the influence of severe in vivo hypoxia (5% O2/95% N2 for 30 min at 22 degrees C). After hypoxia, neuronal damage was observed in the CA3 and dentate gyrus (DG) after 3 and 21 days of survival, but not in the CA1.2,3-Dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline (NBQX), an antagonist for AMPA/kainate receptors, showed neuroprotective effects in the CA3 and DG. These results suggest that hypoxia may induce neuronal damage in the CA3 and DG through activation of AMPA/kainate receptors.

Analysis of Variance↗
PubMed1995

Subcellular localization of the low density lipoprotein receptor-related protein (alpha 2-macroglobulin receptor) in human brain.

The subcellular localization of the alpha 2-macroglobulin receptor, also known as the low density lipoprotein receptor-related protein (LRP), was studied in postmortem human brain tissue by light and electron microscopic immunocytochemistry. A specific monoclonal antibody (A2MR2) against the extracellular alpha-chain of the molecule was utilized. Light microscopically, LRP was detected strongly in neurons, weakly in some glial cells and discontinuously along capillary membranes. At the electron microscopic level, positive reaction products were found to be associated with plasma membranes, ribosomes, lysosomes and lipofuscin granules of neurons, glial cells and pericytes. The results suggest that LRP may have a function, particularly in neurons, of receptor-mediated endocytosis with subsequent lysosomal uptake and degradation of ligands such as alpha 2-macroglobulin proteinase complexes and apolipoprotein E.

Aged↗
PubMed1995

Low-affinity nerve growth factor receptor immunoreactivity in the human urinary bladder.

The localization of low-affinity nerve growth factor receptor (LNGFR) in the human urinary bladder was examined immunohistochemically using the mouse monoclonal antibody (ME20-4) against human LNGFR. LNGFR immunoreactivity was present in the human urinary bladder. The distribution of LNGFR-positive fibers was more abundant in the mucosa than in the muscle layer. Results also showed that some LNGFR-positive fiber bundles contained tyrosine hydroxylase immunoreactivity. Electron microscopic examination revealed that LNGFR immunoreactivity was located on the surface of Schwann cells, and frequently on the interface of axons and Schwann cells.

Adolescent↗
PubMed1995

Actions of acidic fibroblast growth factor fragments on food intake in rats.

Acidic fibroblast growth factor (aFGF) has suppressive effects on food intake. In the present study, the effect of aFGF fragments on food intake were investigated in rats. Infusion of a carboxyl-terminal fragment of aFGF, aFGF-(114-140), did not affect food intake, whereas an amino-terminal fragment of aFGF, aFGF-(1-15), was significantly inhibitory. Other amino-terminal fragments, aFGF-(1-20), aFGF-(1-29) and aFGF-(9-29), did not affect food intake. However, [Ala16]aFGF-(1-29) and [Ser16]aFGF-(1-29) in which the cysteine residue at position 16 was replaced with alanine and serine, respectively, had significant suppressive effects on food intake. Infusion of a functional antagonist for FGF receptor, anti-FGFR-1 antibody, into the lateral hypothalamus (LHA) significantly increased food intake. The results suggest that: the amino-terminal portion of aFGF is active in food intake suppression; the replacement of cysteine residue by alanine or serine is important in some amino-terminal aFGF fragments; and the LHA is involved in feeding suppression actions by aFGF and some fragments.

Alanine↗
PubMed1995

Immunohistochemical localization of glucose transporters (GLUT1 and GLUT3) in the rat hypothalamus.

Immunohistochemical localization of the glucose transporters was studied in the rat hypothalamus by using a specific rabbit antiserum raised against either the isoform 1 (GLUT1) or the isoform 3 (GLUT3). Immunoreactive staining for GLUT1 was found in glia cells and capillaries, whereas positive staining for GLUT3 occurred mainly in neurons and partly in ependymal cells. Double immunostaining indicated that a small population of GLUT1-positive cells were reactive for glial fibrillary acidic protein, a marker for astrocytes. Another doubly stained section showed that GLUT1-positive glia cells were never stained with an OX42 antibody, a marker for microglia cells. Neurons staining positively for GLUT3, often large in cell size, were confined mainly in the lateral hypothalamic area and partly in the dorsomedial and periventricular hypothalamic nuclei. Possible significance of these two glucose transporters in the hypothalamus is briefly discussed.

Amino Acid Sequence↗
PubMed1995

Demonstration of fibroblast growth factor receptor-I in human prostate by polymerase chain reaction and immunohistochemistry.

The expression and localization of fibroblast growth factor receptor-1 were investigated in human prostatic tissues with or without benign hyperplasia. Using a polymerase chain reaction method, we were able to demonstrate that prostatic tissues with benign hyperplasia expressed a significantly higher level of fibroblast growth factor receptor-1 mRNA than normal prostatic tissues (P < 0.01 by Anova). Western blot analysis using an antiserum against the receptor gave 2 bands with molecular weights of about 140 kDa and 80 kDa; these correspond to the expected sizes of the long and secreted forms of the fibroblast growth factor receptor-1, respectively. An immunohistochemical study using the same antiserum further demonstrated that the immunoreactive staining occurred mainly in the basal cells of the glandular epithelium and occasionally in the stromal cells. These results suggest that fibroblast growth factors may influence, at least in part, the proliferation of the epithelial cells seen in benign hyperplasia of human prostate.

Adult↗
PubMed1995

Pick's disease immunohistochemistry: new alterations and Alzheimer's disease comparisons.

Pick's disease (PD) brains were examined immunohistochemically for the expression of antigens known to be associated with Alzheimer's disease (AD) lesions. Most antibodies which label intracellular neurofibrillary tangles (NFTs) in AD were found to stain Pick bodies (PBs). Among them was the monoclonal antibody A2B5, which is known to recognize neuronal surface gangliosides. This result indicates that membrane proteins are probably incorporated into PBs as into NFTs. However, PBs, in contrast to NFTs, showed a paucity of staining for heparan sulfate glycosaminoglycan and basic fibroblast growth factor (bFGF). Staining for midkine, seen in senile plaques in AD, was not seen in PD. The relative lack of staining for these two neurotrophic factors in PD brain may reflect underlying mechanisms which are distinct from those in AD. We also describe two glial abnormalities in PD: glial fibrillary tangles and clusters of granules positive for the complement protein C4d in the hippocampal dentate fascia. These are presumably related to complement-activated oligodendroglia, and both pathological structures are more abundant in advanced cases, suggesting that they may be hallmarks of the disease progression.

Aged↗