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S Itagaki

Publications and source records attributed to S Itagaki.

At least 19 recordsLinked to original sources
PubMed2006

Functional and molecular analysis of D-serine transport in retinal Müller cells.

D-serine, an endogenous co-agonist of NMDA receptors in vertebrate retina, may modulate glutamate sensitivity of retinal neurons. This study determined at the functional and molecular level the transport process responsible for D-serine in retinal Müller cells. RT-PCR and immunoblotting showed that serine racemase (SR), the synthesizing enzyme for D-serine, is expressed in the rMC-1 Müller cell line and primary cultures of mouse Müller cells (1 degrees MCs). The relative contributions of different amino acid transport systems to d-serine uptake were determined based on differential substrate specificities and ion dependencies. D-serine uptake was obligatorily dependent on Na+, eliminating Na+-independent transporters (asc-1 and system L) for D-serine in Müller cells. The Na+:substrate stoichiometry for the transport process was 1:1. D-serine transport was inhibited by alanine, serine, cysteine, glutamine, and asparagine, but not anionic amino acids or cationic amino acids, suggesting that D-serine transport in Müller cells occurs via ASCT2 rather than ASCT1 or ATB0,+. The expression of mRNAs specific for ASCT1, ASCT2, and ATB0,+ was analyzed by RT-PCR confirming the expression of ASCT2 (and ASCT1) mRNA, but not ATB0,+, in Müller cells. Immunoblotting detected ASCT2 in neural retina and in 1 degrees MCs; immunohistochemistry confirmed these data in retinal sections and in cultures of 1 degrees MCs. The efflux of D-serine via ASCT2 by ASCT2 substrates was demonstrable using the Xenopus laevis oocyte heterologous expression system. These data provide the first molecular evidence for SR and ASCT2 expression in a Müller cell line and in 1 degrees MCs and suggest that D-serine, synthesized in Müller cells by SR, is effluxed via ASCT2 to regulate NMDA receptors in adjacent neurons.

Amino Acid Transport System ASC↗
PubMed2001

New anti-malarial flavonol glycoside from Hydrangeae Dulcis Folium.

Bioassay-guided fractionation of the MeOH extract of Hydrangeae Dulcis Folium resulted in isolation of a new flavonol glycoside and two known congeners as anti-malarial principles. These flavonol glycosides showed characteristic proliferation inhibition of Plasmodium falciparum at significantly low concentration without showing any cytotoxicity. In addition, several naturally occurring flavonol glycosides were also shown to exert similar anti-malarial behavior.

Animals↗
PubMed2000

Localization and age-related changes in cytochrome P450 expression in APA hamster livers.

To establish the baseline data, age-related changes and the regional expression of the hepatic P450 isozymes in Syrian hamsters of the APA strain at 3, 6, 12, 18 months old were examined by immunological techniques. Immunohistochemical analysis of liver serial sections revealed that the midzonal and perivenous regions (zones 2 and 3, respectively) were stained with the anti-rat CYP1A1/2, 2B1/2 and 2E1 antibodies. These three antibodies most intensely stained the hepatocytes around the central vein. An anti-rat CYP3A2 staining section had a staining pattern with equally intense reactions in zones 2 and 3. On the other hand, CYP2C6, 2C11 and 4A1 were distributed diffusely throughout the hepatic acinus. There was no age-related difference in the expression pattern of any of the P450 isozymes examined. Total P450 content had a peak at 6 months of age and decreased to 60% of that level thereafter. Western-blot analysis revealed that the peak expressions of the isozymes detected with anti-rat CYP1A1/2, 2C6, 2E1 and 3A2 antibodies were observed in 6-month-old hamsters and declined in older ones. The CYP2B and 2C11 content reached the maximum at the age of 6 months and maintained almost the same level thereafter. The CYP4A level did not change from 3 to 6 months, and then declined to about 40% of the younger level at 12 and 18 months of age. These results suggest that the hepatic P450 isozymes of APA hamsters have region-specific expressions and most isozymes have their peaks of expression at 6 months of age, which differs from the patterns for rat P450.

Aging↗
PubMed2000

Aortic atheromatous lesions developed in APA hamsters with streptozotocin induced diabetes: a new animal model for diabetic atherosclerosis. 1. Histopathological studies.

To develop an adequate animal model for atherosclerosis in large vessels of patients with diabetes, i.e. diabetic macroangiopathy, we induced diabetes in APA hamsters with a single injection of streptozotocin (SZ) and examined the aorta histopathologically and immunohistochemically. As a result, hyperglycemia and hyperlipidemia were continuously observed for 26 weeks after the SZ injection (WAI) in APA hamsters. Fatty streaks characterized by a subendothelial accumulation of many foam cells were observed, limited to the aortic arches as early as 6 WAI. In addition to larger fatty streaks developing with the duration of diabetes, fibrous plaques and plaques containing calcium deposits or cholesterol clefts developed at 26 WAI. These lesions are generally similar to the atheromatous lesions developed in humans. Moreover, depositions of apolipoprotein E and advanced glycation end-products immunohistochemically detected in the lesions were very similar to those found in humans. The diabetic APA hamster is therefore considered to be a useful model for studying the formation of atheromatous lesions in diabetic patients.

Alloxan↗
PubMed2000

APA hamster model for diabetic atherosclerosis. 2. Analysis of lipids and lipoproteins.

Syrian hamsters of the APA strain (APA hamsters) have recently been shown to have atheromatous lesions in the aortic arches under diabetic condition induced by a single injection of streptozotocin (SZ). In that model, fatty streaks, which are the initial lesions of atherogenesis, develop by 6 weeks after the injection (WAI). In this study, we evaluated plasma lipid concentrations and lipoprotein profiles in diabetic APA hamsters at 6 WAI to reveal the early stage of atherogenesis clinicopathologically. As a result, by biochemical analysis, hyperglycemic APA hamsters showed signs of hypercholesterolemia and hypertriglyceridemia. Low-density lipoprotein (LDL) cholesterol significantly increased, but high-density lipoprotein (HDL) cholesterol significantly decreased. Agarose gel electrophoresis showed an obvious increase in the fractions of chylomicron, LDL and abnormal lipoprotein. Plasma LDL in diabetic animals was in a state more susceptible to oxidization. In addition, a significant increase in glycated LDL was also found in the diabetic animals by enzyme linked immunosorbent assay (ELISA). Moreover, lipid peroxidation product (4-hydroxynonenal (4 HNE))-adducted proteins and advanced glycation end-products (AGE) were immunohistochemically detected in the foam cells of the fatty streaks. These results revealed that diabetic APA hamsters had hyperlipidemia characterized by increases in chylomicron, LDL and abnormal lipoprotein, and suggested that oxidized LDL and/or glycated LDL might be actively uptaken by macrophages and play an important role in the initial stage of atherogenesis.

Aldehydes↗
PubMed1999

Pulmonary lesions in guinea pigs experimentally infected with Actinobacillus pleuropneumoniae (A.p.) serovar 1.

Pathological studies were carried out on the lungs of guinea pigs intratracheally inoculated with 4.6 x 10(6-8) colony forming units (CFU)/head of Actinobacillus pleuropneumoniae serovar 1. All animals in the highest dose group died within 24 hr post inoculation (hpi) and showed pulmonary lesions being hemorrhagic in nature while all animals in the lowest dose group were killed as scheduled at 11 days post inoculation (dpi) and showed only hyperplasia of peribronchial lymphoid tissues. In the middle dose group, two died within 24 hpi, two died at 9 dpi, and the remaining one was killed at 11 dpi. Two guinea pigs which died at 9 dpi showed fibrinonecrotic pleuropneumonia which is the most characteristic acute pulmonary lesion in swine, and has not yet been reproduced in laboratory animals up to the present time. This suggests that guinea pigs may be a useful laboratory animal for studying the pathogenesis of Actinobacillus pleuropneumoniae infection in swine.

Actinobacillus Infections↗
PubMed1998

Inhibition of polyposis in the small intestine of BALB/c mice by intestinal bacteria.

The incidence of polyposis and the number of polyps per mouse were significantly lower in conventionalized (CVz) mice than in germ-free (GF) mice. There was no significant difference in the average number of polyps between GF and gnotobiotic (GB) mice monoassociated with the various strains of intestinal bacteria. However, the incidence of polyposis and the number of polyps per mouse were significantly lower for mice associated with either chloroform-resistant bacteria (CRB) or fusiform bacteria (FB) than for GF mice. This study demonstrated that polyposis was suppressed by FB and CRB in the small intestine of BALB/c mice.

Animals↗
PubMed1998

Histochemical and lectinhistochemical studies on nasal mucosa of pigs with or without respiratory diseases.

Histochemical and lectinhistochemical examinations were carried out on nasal mucosa of pigs with or without respiratory diseases. As the results, both acid and neutral mucins coexisted in nasal mucosa of normal pigs while acid sialomucins were mainly observed in nasal mucosa of pigs infected with Bordetella bronchiseptica and/or Pasteurella multocida. Lectinhistochemistry revealed that the nasal epithelial cells of normal pigs were rich in N-acetylgalactosamine, fucose and N-acetyl-glucosamine residues which showed a tendency to disappear in porcine cytomegalovirus infection and to increase in atrophic rhinitis, respectively.

Animals↗
PubMed1998

Age-related changes in major lymphocyte subsets in cynomolgus monkeys.

Age-related changes in major lymphocyte subsets were analyzed in 195 cynomolgus monkeys (Macaca fascicularis) aged from one month to 31 years. The percentages of CD20+ B cells in peripheral blood lymphocytes (PBL) decreased with age to five years of age, but after that, no significant change was observed. The percentages of CD16+ NK cells gradually increased during the first five years and reached the peak at from four to ten years of age, whereas the percentages of CD3+ T cells in PBL were relatively constant throughout the life. Among the T cells, the CD4+ CD8- T cells decreased, but CD4- CD8+ T cells increased within the first decade of life. We further analyzed the expressions of CD28 and CD29 molecules on T cells to determine the relation between age-related activation and phenotypic changes. Almost all CD4+ CD8- T cells (> 90%) were CD28+ at all ages analyzed, but a clear age-related decrease in CD28 expression was demonstrated in CD4- CD8+ T cells during the first ten years. In the case of CD29 expression, age-related increases in CD29hi cells were apparent in both CD4+ CD8- and CD4- CD8+ T cells during the first ten years. The percentages of CD29hi cells, however, were higher in CD4- CD8+ T cells than in CD4+ CD8- T cells in all ages analyzed. These results indicated that the age-related changes in percentages of major lymphocyte subsets as well as in phenotypes of T cells might be related to the maturation of the immune system including an increase in memory cells in cynomolgus monkeys.

Aging↗
PubMed1997

Galactosamine-induced apoptosis in the primary mouse hepatocyte cultures.

Galactosamine (GalN)-induced apoptosis was investigated in cultured hepatocytes from mice. The percentage of fragmented DNA measured by the ELISA method increased in a concentration-dependent manner from the very early stage, i.e. 0.5 hrs, after GalN-exposure. In addition, a ladder-like fragmentation pattern by agarose gel electrophoresis appeared first at 3 hr-exposure to 20 mM GalN, at 6 hr-exposure to 10 mM GalN and at 12 hr-exposure to 5 mM GalN, respectively. On the other hand, cytotoxicity indicated by leakage of lactate dehydrogenase from cultured hepatocytes to culture medium was first detected at 24 hrs after GalN-treatment. Morphologically, formation of blebs and apoptotic bodies was observed from 12 hr-exposure to 20 mM GalN and from 24 hr-exposure to 10 mM GalN, respectively. Thus GalN could induce apoptosis in primary hepatocyte cultures from mice.

Animals↗
PubMed1997

Modification of spontaneous renal lesion of APA hamsters by streptozotocin-induced diabetes.

Syrian hamsters of the APA strain (APA hamsters) develop spontaneous mesangial thickening in the renal glomeruli from an early age. They also develop focal and segmental glomerulosclerosis (FSG) at and after 6 months of age. In this study, histopathological, immunohistochemical and lectin histochemical examinations were conducted to clarify the modification of the spontaneous renal lesions of APA hamsters by streptozotocin(SZ)-induced diabetes. Histopathological analysis revealed that the expansion of the mesangial region was more prominent and the thickening of the glomerular basement membrane (GBM) was weaker in SZ-treated animals than in non-treated ones. Immunohistochemical analysis suggested that type IV collagen and laminin were involved in the expansion of the mesangial region and thickening of the GBM. In lectin histochemical analysis, podocytes, capillary endothelial cells, GBM and a part of mesangial region of SZ-treated animals were positive for RCA120 and GSL-I with neuraminidase-pretreatment although they were negative for these lectins in non-treated animals. These results suggest that the spontaneous glomerular lesion of APA hamsters is modified qualitatively and quantitatively by SZ-induced diabetes.

Animals↗
PubMed1997

Hair follicles of young Wistar strain hairless rats: a histological study.

The histological changes in hair follicles in hairless rats derived from the Wistar strain (hW, hairless Wistar) were examined from birth to maturity and compared with those of age-matched normal Wistar rats. In the 1st hair cycle, the hair follicles of hW rats were shorter and less well developed than those of Wistar rats. In early anagen, eosinophilic bodies were observed in some hair follicles which showed immature histological features. By using Tdt-mediated dUTP nick end labelling (TUNEL) method and electron microscopic examination, these bodies were confirmed to be apoptotic bodies. These follicles seemed to disappear by abnormal regression. In late anagen phase, the follicles in which the apoptosis did not occur showed enlarged hair roots with hypertrophy of the inner root sheath. Subsequently, when the follicles in normal Wistar rats synchronously regressed in the catagen phase, most of the follicles in hW rats similarly entered the catagen phase, but a few follicles did not regress completely and showed aberrant hair root enlargement. Finally, both types of follicle in hW rats formed follicular cysts. These abnormalities in follicle development (abnormal follicular regression and follicular cyst formation) appear to be associated with the hairlessness in this rat strain.

Animals↗
PubMed1997

Replication of feline syncytial virus in feline T-lymphoblastoid cells and induction of apoptosis in the cells.

Feline syncytial virus (FSV) was isolated from feline peripheral blood mononuclear cells of FSV-seropositive cats. When the susceptibility of feline T-lymphocytes to FSV was examined using three strains of FSV, FSV antigens were detected in the FSV-infected T-lymphoblastoid cells. Further, a diversity of biological properties, including replication kinetics and syncytia formation, was noted among the strains, and condensation of chromatin and the fragmentation of cellular DNA were observed in the infected cells. From these data, we conclude that FSV is lymphotropic and can induce apoptosis in the lymphocytes.

Animals↗
PubMed1997

Possible role of macrophage-derived soluble mediators in the pathogenesis of encephalomyocarditis virus-induced diabetes in mice.

Pancreatic islets from DBA/2 mice infected with the D variant of encephalomyocarditis (EMC-D) virus revealed lymphocytic infiltration with moderate to severe destruction of pancreatic beta cells. Our previous studies showed that the major population of infiltrating cells at the early stages of infection is macrophages. The inactivation of macrophages prior to viral infection resulted in the prevention of diabetes, whereas activation of macrophages prior to viral infection resulted in the enhancement of beta-cell destruction. This investigation was initiated to determine whether macrophage-produced soluble mediators play a role in the destruction of pancreatic beta cells in mice infected with a low dose of EMC-D virus. When we examined the expression of the soluble mediators interleukin-1 beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) in the pancreatic islets, we found that these mediators were clearly expressed at an early stage of insulitis and that this expression was evident until the development of diabetes. We confirmed the expression of these mediators by in situ hybridization with digoxigenin-labelled RNA probes or immunohistochemistry in the pancreatic islets. Mice treated with antibody against IL-1beta or TNF-alpha or with the iNOS inhibitor aminoguanidine exhibited a significant decrease in the incidence of diabetes. Mice treated with a combination of anti-IL-1beta antibody, anti-TNF-alpha antibody, and aminoguanidine exhibited a greater decrease in the incidence of disease than did mice treated with one of the antibodies or aminoguanidine. On the basis of these observations, we conclude that macrophage-produced soluble mediators play an important role in the destruction of pancreatic beta cells, resulting in the development of diabetes in mice infected with a low dose of EMC-D virus.

Animals↗
PubMed1997

Apoptosis of murine hepatocytes induced by high doses of galactosamine.

Apoptosis induced by high doses of Galactosamine (GalN) was investigated in mice hepatocytes in vivo. In mice intraperitoneally (i.p.) treated with GalN 3 g/kg, the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells were first observed at 6 hr postadministration (PA). Both acidophilic bodies in hematoxylin and eosin (HE)-stained sections and TUNEL-positive cells were markedly found at 24 hr PA. At 48 hr PA, cellular degeneration and necrosis of hepatocytes were prominently observed, and TUNEL-positive cells were scarcely found. In the mice ip treated with GalN 1.5 g/kg, the lesion was milder than that in those treated with GalN 3 g/kg. Acidophilic bodies and TUNEL-positive cells were scarcely found at 24 hr PA, whereas they were markedly seen at 48 hr PA. In addition, a ladder-like DNA fragmentation pattern by agarose gel electrophoresis was observed most remarkably at 24 hr PA with GalN 3 g/kg and at 48 hr PA with GalN 1.5 g/kg, and less distinctly at 48 hr PA with GalN 3 g/kg. On the other hand, sGOT and sGPT activities increased prominently at 48 hr PA with GalN 3 g/kg. These results suggest that the cell death induced by high dose of GalN may be caused by apoptosis, and subsequently by necrosis in vivo.

Alanine Transaminase↗
PubMed1997

Histological characteristics of respiratory system in Brown Norway rat.

It is well known that the Brown Norway (BN) rat strain exhibits airway hyperresponsiveness to exposure to allergens or some chemicals. We investigated the histological characteristics of the trachea and lungs of this strain (10-week-old and retired animals) and compared them with those of age-matched Fischer 344 (F344) rat strain. No histological differences between two strains in tracheal epithelial cells were detected, but differences in the distribution and development of submucosal glands were clarified by the observation of serial sections cut at intervals of 100 microns. Submucosal glands of BN strain were larger in the number and better-developed than those of F344 strain, especially in the middle and lower trachea. Similar results were also obtained in scanning electron microscopic observation of resin casts. There were no significant differences between two strains in the lectin histochemical characteristics of the cytoplasm of glandular epithelial cells. No age-related changes in these morphological characteristics in the two strains were observed. These results suggest that mucin from submucosal glands is quantitatively different but qualitatively similar in the two strains. In addition, microgranuloma mainly composed of histiocytes and eosinophils was observed in the lungs of the BN strain rats.

Animals↗
PubMed1997

Response of respiratory epithelium of BN and F344 rats to formaldehyde inhalation.

BN rats are well-known for their high capacity for IgE production and hyperresponsiveness to exposure to allergens or other chemicals. We examined the histological changes in the nasal cavity, trachea and lungs of BN and F344 rats after the inhalation of aerosol formaldehyde (HCHO), which exerts direct toxic effects on the respiratory system. The incidence of clinical signs such as sneezing and abnormal respiration in HCHO-treated F344 rats was higher than that in HCHO-treated BN rats. The mean body weight of HCHO-treated F344 rats apparently decreased in comparison with control F344 rats, but that of HCHO-treated BN rats was not significantly different from that of control BN rats. Changes such as squamous metaplasia, stratification, degeneration and desquamation were observed by light microscopy in nasal, tracheal and bronchial mucosa in the lungs of the HCHO-treated F344 rats. In the HCHO-treated BN rats, similar but milder lesions were restricted to the nasal mucosa. Scanning electron microscopic observation supported these light microscopic observations. These results suggest that BN rats have lower sensitivity to HCHO inhalation than F344 rats.

Administration, Inhalation↗