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A Ota

Publications and source records attributed to A Ota.

At least 19 recordsLinked to original sources
PubMed2003

Effect of peripheral lipopolysaccharide injection on dopamine content in murine anterior olfactory nucleus.

Norepinephrine turnover rate in the murine locus coeruleus (LC) is known to be enhanced by the intraperitoneal (i.p.) injection of lipopolysaccharide (LPS). Approximately 40% of LC neurons are also known to project to the olfactory bulb (OB) and the anterior olfactory nucleus (AON). Therefore, we investigated whether an i.p. injection of 500 microg LPS could modulate the catecholamine biosynthesis in these sites in 8-week-old C3H/HeN male mice. Unexpectedly, the content of norepinephrine was not elevated in both sites during 6-h-observation after LPS injection. The contents of dopamine and its metabolites in the AON were highly increased at 4 h after LPS injection, whereas those in the OB were not elevated during 6-h-observation. Although the AON has been considered not to belong to the dopaminergic neuron system, our report is the first to show an elevated dopamine content in the AON under a stressful condition such as endotoxemia.

Animals↗
PubMed2003

Peripheral administration of lipopolysaccharide enhances the expression of guanosine triphosphate cyclohydrolase I mRNA in murine locus coeruleus.

GTP cyclohydrolase I is the first and rate-limiting enzyme for the de novo biosynthesis of tetrahydrobiopterin, which is the cofactor for tyrosine hydroxylase. Lipopolysaccharide can modulate tetrahydrobiopterin production by upregulating GTP cyclohydrolase I protein expression in the locus coeruleus in the mouse brain. The increased supply of tetrahydrobiopterin in the locus coeruleus leads to increased tyrosine hydroxylase activity without affecting the level of tyrosine hydroxylase protein expression, resulting in an increase in norepinephrine turnover at the site. This study was performed to address whether the increase in GTP cyclohydrolase I protein is dependent on the de novo synthesis of GCH in the locus coeruleus. After i.p. administration of lipopolysaccharide, the mRNA expression of GTP cyclohydrolase I was examined. The expression level increased within 2 h, and reached to maximum level at 4 h after the lipopolysaccharide administration. However, the mRNA expression level of 6-pyruvoyl-tetrahydropterin synthase and sepiapterin reductase, both of which are involved successively after GTP cyclohydrolase I in tetrahydrobiopterin biosynthesis, were not affected by the lipopolysaccharide administration. These results suggest that GTP cyclohydrolase I upregulation alone is enough to modulate tetrahydrobiopterin production in the locus coeruleus. In addition, the mRNA level of tyrosine hydroxylase was also not affected by the lipopolysaccharide administration. Taken together, the data indicate that GTP cyclohydrolase I plays a crucial role in regulating norepinephrine biosynthesis by a pathway the activity of which is triggered by lipopolysaccharide i.p. administration.

Alcohol Oxidoreductases↗
PubMed2001

Expression of GTP cyclohydrolase I in murine locus ceruleus is enhanced by peripheral administration of lipopolysaccharide.

Among the enzymes involved in the system for catecholamine biosynthesis, GTP cyclohydrolase I (GCH) contributes to the system as the first and rate-limiting enzyme for the de novo biosynthesis of tetrahydrobiopterin (BH4), which is the cofactor for tyrosine hydroxylase (TH). Therefore, we investigated whether the endotoxemia caused by an intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) can modulate BH4 production in the norepinephrine nuclei, i.e. the locus ceruleus (LC; A6) and central caudal pons (A5), in C3H/HeN mice and whether such a change in BH4, if any, can result in the modification of norepinephrine production in these nuclei. After a 5-microg i.p. injection of LPS, the protein expression of GCH and TH in both nuclei was examined by immunohistochemistry. The staining intensity of GCH-positive cells increased at 6 h, whereas no significant change in the staining intensity of TH-positive cells was detected. Next, we measured the contents of BH4, norepinephrine, and its metabolites 4-hydroxy-3-methoxyphenylglycol (MHPG) and DL-4-hydroxy-3-methoxymandelic acid (VMA) in these nuclei after LPS i.p. injection. The BH4 content increased to a statistically significant level at 2 and 4 h after the injection. The contents of MHPG and VMA also showed a time-course similar to that of BH4. These data can be rationalized to indicate that an increased supply of BH4 in the LC increased TH activity and resulted in an increase in norepinephrine production rate at the site. This is the first report that sheds light on BH4 as a molecule that intervenes during endotoxemia to increase norepinephrine production rate in the LC.

Animals↗
PubMed2001

A new reconstructive procedure after segmental pancreatectomy: an experimental study of pancreatic end-to-end (duct-to-duct) anastomosis.

We produced experimental models of pancreatic end-to-end anastomosis, including ductal end-to-end anastomosis (with or without stent) and pancreaticojejunostomy, using mongrel dogs, with a view to evaluating reconstructive procedures after segmental pancreatectomy. We examined macroscopic findings, pancreatograms, and microangiographic and histopathological findings to determine whether pancreatic end-to-end anastomosis was as practicable as pancreaticojejunostomy. Macroscopic findings showed no suture failure in any animal in the end-to-end anastomosis group. Pancreatography revealed obstruction of the stent tube in the stent subgroup, but good patency in the no-stent subgroup. On the imaging of the microvasculature in the end-to-end anastomosis group, proliferation of neovascular vessels and formation of communicating vessels were detected. Histopathologically, no suture failure was detected, and the viability of the pancreatic end-to-end anastomosis was confirmed. From this experiment, we concluded it that it was possible to employ pancreatic end-to-end anastomosis after segmental pancreatectomy in the clinical situation.

Anastomosis, Surgical↗
PubMed2001

Determination of tetrahydrobiopterin in murine locus coeruleus by HPLC with fluorescence detection.

Tetrahydrobiopterin in the murine locus coeruleus was measured as its fully oxidized form, biopterin, using a HPLC coupled to a fluorescence detector, because tetrahydrobiopterin itself cannot be detected by such means. The differential oxidization method distinguished tetrahydrobiopterin-derived biopterin and dihydrobiopterin-derived biopterin. The protocol reported here is a rapid and sensitive method that facilitates the measurement of tissue and/or cellular tetrahydrobiopterin. Using this assay protocol, we were able to detect and quantify variations in the tetrahydrobiopterin content in the murine locus coeruleus.

Animals↗
PubMed2001

Exon 3 of tyrosine hydroxylase gene: lack of association with Japanese schizophrenic patients.

Tyrosine hydroxylase (TH) is the rate-limiting enzyme in dopamine (DA) biosynthesis. Exon 3 of the human TH gene encodes the sequence from Ser31 to Glu104 of type 1 enzyme, which contains the critical parts for regulation of the catalytic activity. The amino acid residues Gly36-Arg37-Arg38 were identified as a key sequence for DA to exert its inhibitory effect on catalytic activity. Therefore, we screened the nucleotide sequences of exon 3 from 201 Japanese patients with schizophrenia to explain the elevation in the synaptic or presynaptic DA concentrations in the schizophrenic brain, based on the hypothesis that any mutation changing the amino acid sequence Gly36-Arg37-Arg38 would result in the elevation of DA synthesis, due to a reduced inhibitory effect of DA on the catalytic activity. However, no mutated sequences of exon 3 and both exon-intron boundaries were detected in any of the patients examined. Polymorphisms generating Val81 and Met81 were compared of the distributions of genotype and allele between the patients and 175 Japanese healthy controls, which did not suggest an association between the polymorphism and schizophrenia. These results indicate that exon 3 of the human TH gene lacks association with schizophrenia in Japanese patients.

Adult↗
PubMed2001

Platelet activating factor degradation in tear fluid from guinea pigs with allergic conjunctivitis.

The purpose of this study was to investigate the role of platelet-activating factor (PAF) and PAF acetylhydrolase (AH) in conjunctiva. The influence of PAF on conjunctival vascular permeability and the presence of PAF or its metabolites in tears from guinea pigs with allergic conjunctivitis were investigated. We instilled PAF to the eyes of guinea pigs and evaluated vascular permeability. Tear samples were collected from passively sensitized guinea pigs, and the concentration of PAF and its metabolites determined by liquid chromatography-tandem mass spectrometry. Exogenous PAF degradation in tear samples was evaluated with or without diisopropyl fluorophosphate (DFP). Topically applied PAF increased vascular permeability in conjunctiva. In the tear samples from guinea pigs with allergic conjunctivitis, PAF could not be detected. However, 40 +/- 6 ng/ml of lyso-platelet activating factor (lyso-PAF) and 230 +/- 50 ng/ml of 1-alkyl-2-acyl-sn-glycero-3-phosphocholine were detected at 10 min after challenge. Exogenous PAF was rapidly degraded in the tear samples from guinea pigs with allergic conjunctivitis, but not from normal guinea pigs. This PAF degradation was inhibited by DFP. These results suggest that PAF in the tear fluid is quickly hydrolyzed to lyso-PAF by PAF AH, which may be released or activated in allergic conjunctivitis.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2001

[Successful treatment of refractory idiopathic thrombocytopenic purpura by eradication of Helicobacter pylori].

A 53-year-old woman was diagnosed as having idiopathic thrombocytopenic purpura (ITP) in 1990, and treated with prednisolone and splenectomy, which did not result in remission. In November 2000, gastrointestinal endoscopy showed superficial gastritis, and Helicobacter pylori infection was revealed by the rapid urease test and histologic examination. After eradication of Helicobacter pylori by amoxicillin, clarithromycin and lansoprazole, the patient's platelet count was increased from 24 x 10(9)/l to 134 x 10(9)/l and platelet-associated IgG (PAIgG) was decreased from 695 ng/10(7) cells to 33 ng/10(7) cells. This case suggests that eradication of Helicobacter pylori may be useful for treating some patients with refractory ITP.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2000

Positive charge intrinsic to Arg(37)-Arg(38) is critical for dopamine inhibition of the catalytic activity of human tyrosine hydroxylase type 1.

Tyrosine hydroxylase (TH), which converts L-tyrosine to L-3, 4-dihydroxyphenylalanine, is a rate-limiting enzyme in the biosynthesis of catecholamines; its activity is regulated by the feedback inhibition of the catecholamine products including dopamine. To rationalize the significant role of the N-terminal sequence Arg(37)-Arg(38) of human TH type 1 (hTH1) in determining the efficiency of feedback inhibition, we produced mutants of which the positively charged Arg(37)-Arg(38) site was replaced by electrically neutral Gly and/or negatively charged Glu and analyzed the degree of inhibition of these mutant enzymes by dopamine. The replacement of Arg by Gly reduced the inhibitory effect of dopamine on the catalytic activity measured in the basic pH range and the replacement of Arg by Glu was enough to abolish the inhibitory effect, although these mutations brought no significant changes to the circular dichroism spectrum. The prediction of the secondary structure of N-terminal residues 1-60 by computer software specified the location of the Arg(37)-Arg(38) sequence in the turn intervening between the two alpha-helices (residues 16-29 and residues 41-59). These results suggest that the positive charge of the amino acid residues at positions 37 and 38 is one of the main factors that maintains the characteristic of the turn and is responsible for the enzyme inhibition by dopamine.

Amino Acid Sequence↗
PubMed1999

Expression of human tyrosine hydroxylase type I in Escherichia coli as a protease-cleavable fusion protein. Short communication.

Wild-type and N-terminal 35-, 38-, and 44-amino acid-deleted mutants of human tyrosine hydroxylase type 1 (hTH1) fused to maltose-binding protein via the target sequence for a restriction protease were expressed in Escherichia coli and purified. The fused protein was treated with the restriction protease factor Xa or enterokinase to isolate hTH1 from the fused form. The treatment of fused wild-type and 35-amino acid-deleted mutant with factor Xa and enterokinase caused non-specific cleavages in the vicinity of the phosphorylation sites, Ser19 and Ser40, due to the flexible conformation of the N-terminus of hTH1.

ATP-Binding Cassette Transporters↗
PubMed1999

Heat shock protein 70 and heat shock cognate protein 70 messenger ribonucleic acid induction in the brains, hearts, and livers of neonatal rats after hypoxic stress.

OBJECTIVE: The aim of this study was to examine the production of 2 types of heat shock protein 70 in the organs of neonatal rats during an episode of mild hypoxic stress that was insufficient to produce histologic changes. STUDY DESIGN: Seven-day-old rats were subjected to hypoxia (inspired gas of 8% oxygen and 92% nitrogen) at 33 C for 2 hours (n = 5), 3 hours (n = 5), and 4 hours (n = 5). Control rats (n = 5) inspired room air for 4 hours. The brains, hearts, and livers were removed after 4 hours of recovery. The levels of heat shock protein 70 and heat shock cognate protein 70 messenger ribonucleic acid were measured by Northern blot analysis. Arterial pH, Pao 2, PACO 2, and brain temperature were measured before, during, and at 4 hours of hypoxia in another 16 animals. Histologic examinations were carried out in these 16 animals 7 days after hypoxic stress. RESULTS: PaO 2, PACO 2, and brain temperature decreased during the hypoxic stress and returned to prehypoxic values at recovery time. Arterial pH did not change. No histologic changes were observed in any areas of the brain. Heat shock cognate protein 70 messenger ribonucleic acid was normally expressed in the brain, heart, and liver and was further induced after hypoxia in the brain and the heart. There was, however, no additional increase of heat shock cognate protein 70 messenger ribonucleic acid in the liver. there were no increments of the stress-induced form of heat shock protein 70 messenger ribonucleic acid in these organs. CONCLUSION: Mild hypoxia selectively induced messenger ribonucleic acid of heat shock cognate protein 70, which may play an important role in protecting the brain and the heart against stress.

Animals↗
PubMed1999

Pretreatment with magnesium sulfate protects against hypoxic-ischemic brain injury but postasphyxial treatment worsens brain damage in seven-day-old rats.

OBJECTIVE: Our purpose was to study the neuroprotective effect of magnesium sulfate on hypoxicischemic brain damage and how the timing of magnesium administration changes its effect in the newborn rat. STUDY DESIGN: Seven-day-old rats (n = 91) were exposed to unilateral carotid artery ligation followed by 2 hours of hypoxia (8% oxygen in 92% nitrogen). Magnesium sulfate (270 mg/kg) was intraperitoneally administered 30 minutes before (pretreatment) or 30 minutes after (posttreatment) the 2 hours of hypoxia. In each experiment equivalent amounts of saline solution were administered as controls. Seven days after the injury the rats were killed and the brains were removed for histologic study with hematoxylin and eosin staining. The severity of brain atrophy and neuronal damage was evaluated in the cerebral cortex and hippocampus and compared by chi2 test between the magnesium group and the controls. RESULTS: Ionized magnesium concentrations were significantly increased from 0.52 +/- 0.02 mmol/L to 1.38 +/- 0.07 mmol/L at 0.5 hour after injection and thereafter gradually decreased to 0.73 +/- 0.07 mmol/L at 3.5 hours. Magnesium significantly reduced the incidence of weight loss (0% in magnesium vs 29% in controls) and protected the cerebral cortex from neuronal loss (the incidence of normal, mild, moderate, and severe neuronal loss was 48%, 29%, 5%, and 19% in magnesium and 30%, 5%, 25%, and 40% in controls, respectively) in the pretreatment group. In the posttreatment group magnesium caused increased neuronal damage compared with the controls. CONCLUSION: Magnesium sulfate has neuroprotective effects against hypoxia-ischemia. This effect is restricted to the pretreatment group in which magnesium sulfate is administered before the insult.

Animals↗
PubMed1999

Heat shock protein 72 expression and microtubule-associated protein 2 disappearance after hypoxia-ischemia in the developing rat brain.

OBJECTIVE: This study was intended to investigate the temporal changes in heat shock protein 72 expression and microtubule-associated protein 2 disappearance in rat brain at 2 different ages after hypoxic-ischemic insult. STUDY DESIGN: Both 5-day-old and 14-day-old Wistar rats were subjected to unilateral common carotid artery ligation and hypoxia in 8% oxygen for 2 hours at 33 degrees C. Brain sections were examined sequentially for heat shock protein 72 expression at 0.5, 3, 6, 12, 24, 48, and 72 hours of recovery after hypoxia-ischemia and for microtubule-associated protein 2 disappearance at 0, 24, 48, and 72 hours of recovery and at 7 days of recovery after hypoxia-ischemia. Results of immunohistochemical staining for heat shock protein 72 and microtubule-associated protein 2 were used as markers for detection of early hypoxic-ischemic brain damage. Permanent neuronal damage was assessed with hematoxylin and eosin staining at 7 days after hypoxia. RESULTS: In 5-day-old rats microtubule-associated protein 2 expression was lost as early as 0 hours after hypoxia-ischemia in the cerebral cortex and hippocampus, with a peak at 48 hours after which expression recovered. Expression of heat shock protein 72 was detected in the ligated hemisphere at 0.5 hours after hypoxia-ischemia and peaked at 6 to 24 hours of recovery. In 14-day-old rats microtubule-associated protein 2 was stained in the cortex at 0 hours after hypoxia-ischemia but gradually disappeared in the cerebral cortex and hippocampus after 24 hours of recovery. The expression of heat shock protein 72 was not detected by 6 hours of recovery in the cerebral cortex and by 3 to 12 hours of recovery in the hippocampus, but heat shock protein 72 was persistently expressed in the cortex and hippocampus after 48 hours of recovery. Neuronal damage was significantly less in 5-day-old rats than in 14-day-old rats. CONCLUSION: In 5-day-old rats hypoxia-ischemia causes earlier changes in heat shock protein 72 and microtubule-associated protein 2 immunostaining results and causes less severe brain damage than in 14-day-old rats.

Aging↗
PubMed1999

Dopamine inhibition of human tyrosine hydroxylase type 1 is controlled by the specific portion in the N-terminus of the enzyme.

Tyrosine hydroxylase (TH), which converts L-tyrosine to L-DOPA, is a rate-limiting enzyme in the biosynthesis of catecholamines; its activity is regulated by feedback inhibition by catecholamine products including dopamine. To investigate the specific portion of the N-terminus of TH that determines the efficiency of dopamine inhibition, wild-type and N-terminal 35-, 38-, and 44-amino acid-deleted mutants (del-35, del-38, and del-44, respectively) of human TH type 1 were expressed as a maltose binding protein fusion in Escherichia coli and purified as a tetrameric form by affinity and size-exclusion chromatography. The fused-form wild-type enzyme possessed almost the same specific enzymatic activity as the previously reported recombinant nonfused form. Although maximum velocities of all N-terminus-deleted forms were about one-fourth of the wild-type value, there was no difference in Michaelis constants for L-tyrosine or (6R)-(L-erythro-1',2'-dihydroxypropyl)-2-amino-4-hydroxy-5,6,7,8-tetrahy dropteridine (6RBPH4) among the four enzymes. The iron contents incorporated into the three N-terminus-deleted mutants were significantly lower than that of wild type. However, there was no substantial difference in incorporated iron contents among the three mutants. The deletion of up to no less than 38 amino acid residues in the N-terminus made the enzyme more resistant to dopamine inhibition than the wild-type or del-35 TH form. Dopamine bound to the del-38 more than to the del-35 TH form. However, when incubation with dopamine was followed by further inhibition with the cofactor 6RBPH4 dopamine was expelled more readily from the del-38 than from the del-35 TH form. These observations suggest that the amino acid sequence Gly36-Arg37-Arg38 plays a key role in determining the competition between dopamine and 6RBPH4 and affects the efficiency of dopamine inhibition of the catalytic activity.

Catalysis↗
PubMed1999

Protection against an infectious disease by enterohaemorrhagic E. coli 0-157.

Preventive measures against infection by enterohaemorrhagic E. coli 0-157 are described. Eating yoghurt and Kefir supposedly induces more bifid bacteria and lactic acid bacteria to colonize in the intestines, thereby protecting humans from infection by E. coli 0-157. Some foods, such as plum extract, act as a mild antibiotic and produce an acidic environment within the intestine, thus interfering with growth of the E. coli 0-157. The natural colonization of harmless E. coli or other bacteria that are more powerful than E. coli 0-157 can possibly protect against infection. A vaccination against E. coli 0-157 H7 may also be effective. In addition, it has been suggested that the correct levels of nitric oxide and calcium in the blood may activate immunity and protect against infection by E. coli 0-157.

Escherichia coli O157↗
PubMed1999

Inhibitory mechanism of anti-P30-52 monoclonal antibody against human immunodeficiency virus type 1 (HIV-1) multiplication in infected MT-4 cells.

We have studied the immunological role of human immunodeficiency virus type 1 (HIV-1) p17 because the p17 antibody titer is high in asymptomatic patients and decreases with disease progression. Previously we found that monoclonal antibody (MAb) reactive to the p17-derived peptide 30 to 52 amino acids in length, namely P30-52 MAb, had cross-reactivity to the third variable region of the envelope glycoprotein of HIV-1 (Env V3) and also inhibited the viral multiplication of the supernatant of HIV-1-infected MT-4 cells co-cultured with the MAb. The relation between the cross-reactivity of the P30-52 MAb and the inhibitory mechanism is not clear; however, P30-52 might be useful for the development of therapeutic and vaccination strategies. In the present study, we examined the suppressive mechanism of the P30-52 MAbs, and found that the copy number of HIV-1 RNA in HIV-1-infected MT-4 cells was not reduced by the addition of the P30-52 MAbs, and the expression of RNAs of p17 was slightly enhanced 3 hr after the infection, although that of Env V3 was the same as the control level. In contrast, the expression of cellular p17 DNA and p17 protein was reduced by the addition of the P30-52 MAbs. In conclusion, the P30-52 MAbs did not suppress the HIV-1 mRNA level in the infected cells, but might inhibit DNA synthesis, and consequently bring about a reduction of p17 protein synthesis and a decrease of infectivity of the supernatant. The results demonstrated that the P30-52 MAb could be used as immunotherapeutic substance for HIV-1.

Animals↗