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Biomedical subjects

Hiroyuki Arai

Publications and source records attributed to Hiroyuki Arai.

At least 73 records · Page 4Linked to original sources
PubMed2005

The role of two CbbRs in the transcriptional regulation of three ribulose-1,5-bisphosphate carboxylase/oxygenase genes in Hydrogenovibrio marinus strain MH-110.

Hydrogenovibrio marinus MH-110 possesses three different sets of genes for ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO): two form I (cbbLS-1 and cbbLS-2) and one form II (cbbM). We have previously shown that the expression of these RubisCO genes is dependent on the ambient CO2 concentration. LysR-type transcriptional regulators, designated CbbR1 and CbbRm, are encoded upstream of the cbbLS-1 and cbbM genes, respectively. In this study, we revealed by gel shift assay that CbbR1 and CbbRm bind with higher affinity to the promoter regions of cbbLS-1 and cbbM, respectively, and with lower affinity to the other RubisCO gene promoters. The expression patterns of the three RubisCOs in the cbbR1 and the cbbRm gene mutants showed that CbbR1 and CbbRm were required to activate the expression of cbbLS-1 and cbbM, respectively, and that neither CbbR1 nor CbbRm was required for the expression of cbbLS-2. The expression of cbbLS-1 was significantly enhanced under high-CO2 conditions in the cbbRm mutant, in which the expression of cbbM was decreased. Although cbbLS-2 was not expressed under high-CO2 conditions in the wild-type strain or the single cbbR mutants, the expression of cbbLS-2 was observed in the cbbR1 cbbRm double mutant, in which the expression of both cbbLS-1 and cbbM was decreased. These results indicate that there is an interactive regulation among the three RubisCO genes.

Bacterial Proteins↗
PubMed2005

Inhibition of cholesterol biosynthesis by 25-hydroxycholesterol is independent of OSBP.

25-hydroxycholesterol (25-HC) is a potent suppressor of cholesterol synthesis gene transcription in cultured cells. A high affinity binding protein for 25-HC, oxysterol-binding protein (OSBP), has been identified from tissue cytosol. OSBP translocates from the cytosol to the Golgi apparatus membranes after addition of 25-HC to cell cultures and is thought to mediate 25-HC action on cholesterol metabolism through association to the Golgi apparatus. However, direct evidence to prove this hypothesis was lacking. In this study, we knocked down expression of OSBP by using duplex siRNAs specific for OSBP to examine the relationship between OSBP and 25-HC-induced inhibition of cholesterol synthesis gene transcription. We found that decreasing OSBP expression by approximately 90% did not affect 25-HC-induced inhibition of transcription of 3-hydoxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and squalene epoxidase to any extent. Exogenous lysophosphatidylcholine (LPC), which is known to cause the efflux of cellular cholesterol into the medium and to increase cholesterol synthesis, was found to rescue the 25-HC-induced down-regulation of sterol regulated genes, while LPC did not affect 25-HC-induced association of OSBP with the Golgi apparatus. These results suggest that inhibition of cholesterol biosynthesis genes by 25-HC is OSBP-independent.

Cholesterol↗
PubMed2005

Factors associated with suicidal ideation in an elderly urban Japanese population: a community-based, cross-sectional study.

The objective of the present study was to evaluate the association between suicidal ideation and potentially related factors in an elderly urban Japanese population. This was a community-based, cross-sectional study. Urban community residents aged 70 years or more were interviewed regarding suicidal ideation and sociodemographic and health-related variables. Subjects with depressive symptoms underwent further evaluation by psychiatrists using criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition. Associations were evaluated using univariate and multivariate logistic regression analyses. Of the 1145 eligible participants, 52 (4.5%) reported thoughts of suicide. Of 143 subjects with depressive symptoms (Geriatric Depression Scale, 14+), 22 (15.4%) reported suicidal ideation over a 2-week period. After controlling for depressive symptoms, lack of social support and impaired instrumental activities of daily living were significantly associated with thoughts of suicide. After controlling for the potentially associated factors detected in the univariate analysis, depressive symptoms were strongly associated with thoughts of suicide. In the elderly with depressive symptoms, mental disorders, including depressive and alcohol-related disorders, were significantly associated with suicidal ideation over a 2-week period. In the urban community setting, screening for lack of social support, impaired instrumental activities of daily living, and depressive symptoms, followed by diagnostic evaluation for mental disorders, particularly for depressive syndromes and alcohol-related disorders, may provide a practical and effective means of identifying elders at high risk of suicide.

Aged↗
PubMed2005

Transcriptional regulation of the flavohemoglobin gene for aerobic nitric oxide detoxification by the second nitric oxide-responsive regulator of Pseudomonas aeruginosa.

The regulatory gene for a sigma54-dependent-type transcriptional regulator, fhpR, is located upstream of the fhp gene for flavohemoglobin in Pseudomonas aeruginosa. Transcription of fhp was induced by nitrate, nitrite, nitric oxide (NO), and NO-generating reagents. Analysis of the fhp promoter activity in mutant strains deficient in the denitrification enzymes indicated that the promoter was regulated by NO or related reactive nitrogen species. The NO-responsive regulation was operative in a mutant strain deficient in DNR (dissimilatory nitrate respiration regulator), which is the NO-responsive regulator required for expression of the denitrification genes. A binding motif for sigma54 was found in the promoter region of fhp, but an FNR (fumarate nitrate reductase regulator) box was not. The fhp promoter was inactive in the fhpR or rpoN mutant strain, suggesting that the NO-sensing regulation of the fhp promoter was mediated by FhpR. The DNR-dependent denitrification promoters (nirS, norC, and nosR) were active in the fhpR or rpoN mutants. These results indicated that P. aeruginosa has at least two independent NO-responsive regulatory systems. The fhp or fhpR mutant strains showed sensitivity to NO-generating reagents under aerobic conditions but not under anaerobic conditions. These mutants also showed significantly low aerobic NO consumption activity, indicating that the physiological role of flavohemoglobin in P. aeruginosa is detoxification of NO under aerobic conditions.

Aerobiosis↗
PubMed2005

Plasma homocysteine and risk of coexisting silent brain infarction in Alzheimer's disease.

BACKGROUND: Cerebrovascular disease is common in Alzheimer's disease (AD). Elevated plasma homocysteine (pHcy) levels are reported to be associated with an increased risk of poor cognition and dementia. OBJECTIVE: To determine whether high pHcy levels are associated with an increased risk of coexisting silent brain infarctions (SBIs) in AD. METHODS: Study population comprising 143 outpatients with clinical diagnosis of probable AD (73.3 +/- 7.0 years) were classified into 2 groups according to the presence or absence of SBIs on magnetic resonance imaging. RESULTS: SBIs were noted in 32.9% (47/143) of the AD patients. The pHcy levels in the AD with SBIs (14.0 +/- 4.5 micromol/l) were significant ly elevated compared with the AD without SBIs (11.7 +/- 4.7 micromol/l, p = 0.007). After adjusting for age and gender, high pHcy (>12.4 micromol/l), but not hypertension, was associated with an increased risk of developing SBIs in AD (OR = 4.61, 95% CI = 1.74-12.2, p = 0.002). However, age at onset, cognitive function, cerebrospinal tau or amyloid beta-peptide(1-42) levels were not significantly correlated with pHcy levels in AD. CONCLUSION: SBIs commonly coexist with AD, and may be a unique vascular condition in which homocysteine plays an important role. Homocysteine-lowering therapy rather than antihypertensive medication might be an appropriate strategy to prevent stroke associated with AD.

Aged↗
PubMed2005

Two tandemly arranged ferredoxin genes in the Hydrogenobacter thermophilus genome: comparative characterization of the recombinant [4Fe-4S] ferredoxins.

A thermophilic, obligately chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, assimilates carbon dioxide via the reductive tricarboxylic acid cycle. A gene encoding a ferredoxin involved in this cycle as an electron donor (HtFd1) was cloned and sequenced. Interestingly, another ferredoxin gene (encoding HtFd2) was found in tandem with the HtFd1 gene. These two ferredoxin genes overlapped by four bp, and transcriptional analysis revealed that they are co-transcribed as an operon. The deduced amino acid sequences of HtFd1 and HtFd2 were 42.9% identical and each contained four cysteine residues that serve as probable ligands to an iron-sulfur cluster. Spectroscopic analyses of the purified recombinant ferredoxins heterologously expressed in Escherichia coli indicated that each ferredoxin contains a single [4Fe-4S]2+/1+ cluster.

Amino Acid Sequence↗
PubMed2005

Cognitive decline in patients with long-term domiciliary oxygen therapy.

Cognitive and psycho-physiological condition in patients with long-term domiciliary oxygen therapy (DOT) remains uncertain. A cross sectional analysis was performed to investigate the age-related changes in cognitive and psycho-physiologic functions in patients with chronic respiratory failure receiving long-term DOT. Two expert practitioners visited the patient's home and examined them for analysis of cognitive function, emotional status, physical activity and degree of dyspneic sensation. One hundred and thirty-five patients completed the study. Control data from a cohort of 718 community dwellers were also included in this study. Male patients had significantly higher rates of chronic obstructive pulmonary disease (71% vs 47%, p = 0.001), lower values of forced expiratory volume in one second (FEV1.0) % (49.7 +/- 10.3 [standard deviation, S.D.] vs 66.0 +/- 7.5% predicted, p = 0.002) and higher Borg score, an indicator of dyspneic sensation, during daily exercise (3.2 +/- 0.8 [S.D.] vs 1.4 +/- 0.6, p = 0.01) compared with female patients. Linear regression analysis based on mean Mini-Mental State Examination scores, an indicator of cognitive function, showed that age-related cognitive decline was more pronounced in female patients than in female controls (-0.524/year, R2 = 0.426 vs -0.120/year, R2 = 0.027, p < 0.0001), while there was no significant difference between male patients and male controls (-0.156/year, R2 = 0.054, vs -0.077/year, R2 = 0.016, p = 0.231). These results demonstrate that age-related cognitive decline is more exaggerated in female patients receiving long-term DOT which should be taken into consideration in caring for patients with chronic respiratory failure.

Age Factors↗
PubMed2005

Risk of falls in Alzheimer's disease: a prospective study.

OBJECTIVE: Falls are common in patients with Alzheimer's disease (AD). Identification of the potential risk factors and developing preventive strategies for falls will have a significant impact in maintaining the quality of life in AD. PATIENTS: Clinical follow-up of 124 (74.1+/-6.1 years, range 62-88) mild to moderate AD patients in an outpatient memory clinic. METHODS: Postural sway, cognitive function, use of neuroleptics, severity of periventricular and deep white matter lesions, and the presence or absence of silent brain infarctions on magnetic resonance imaging were assessed at baseline. RESULTS: A total of 104 patients (84%) completed the study. Fall events were confirmed in 42.3% (44/104). After adjustment for age, gender, and cognitive status, a high grade of periventricular white matter lesions (odds ratio 8.7 [95%CI 1.5 to 51.8], p = 0.017) and neuroleptic drug use (odds ratio 3.5 [95%CI 1.2 to 10.5], p = 0.027) were significantly associated with an increased risk of falls. CONCLUSION: Our results suggest that periventricular white matter lesions and the use of neuroleptics may be related to falls in mild to moderate AD. A comprehensive risk management of brain ischemia as well as the use of the smallest efficacious dose of neuroleptics in the treatment of behavioral and psychiatric symptoms of AD should be recommended to help reduce the risk of unexpected falls.

Accidental Falls↗
PubMed2005

A randomized, observer-blind, controlled trial of the traditional Chinese medicine Yi-Gan San for improvement of behavioral and psychological symptoms and activities of daily living in dementia patients.

OBJECTIVE: This randomized, observer-blind, controlled trial examined the efficacy and safety of the traditional Chinese herbal medicine Yi-Gan San (YGS, Yokukan-San in Japanese) in the improvement of behavioral and psychological symptoms of dementia (BPSD) and activities of daily living (ADL). METHOD: Fifty-two patients with mild-to-severe dementia (24 men and 28 women, mean +/- SD age = 80.3 +/- 9.0 years) according to DSM-IV criteria were investigated. Participants were randomly assigned to the YGS group (N = 27) or control (drug-free) group (N = 25) and treated for 4 weeks. The Neuropsychiatric Inventory (NPI) for the assessment of BPSD, the Mini-Mental State Examination (MMSE) for cognitive function, and the Barthel Index for ADL were administered at baseline and the end of the treatment. The frequency of extrapyramidal symptoms (EPS) and other adverse events was recorded. If patients showed insufficient response to treatment after 1 week, tiapride hydrochloride, a dopamine D(1) selective neuroleptic, was added to the regimen. Data were collected from January 2004 to March 2004. RESULTS: All participants in both groups completed the trial. In the control group, 11 patients required treatment with tiapride hydrochloride. Significant improvements in mean +/- SD NPI (from 37.9 +/- 16.1 to 19.5 +/- 15.6) and Barthel Index (from 56.4 +/- 34.2 to 62.9 +/- 35.2) scores were observed in the YGS group, but not in the control group. MMSE results were unchanged in both groups. EPS were not observed in either group, but dizziness and impaired postural sway were observed in 6 patients treated with tiapride hydrochloride. CONCLUSION: Yi-Gan San improves BPSD and ADL. Follow-up studies using a double-blinded, placebo-controlled design are recommended.

Activities of Daily Living↗
PubMed2005

[A proposal for diagnostic and clinical assessment criteria for Alzheimer's disease].

To clarify the risk and associated genes of Alzheimer's disease by genome-wide screening, a Japanese study group was organized in 2000 under Yasuo Ihara, Tokyo University, supported by a Grant-in-Aid for Science Research on Priority Areas (C) -Advanced Brain Science Project from Ministry of Education, Culture, Sports, Science and Technology, Japan. This is the first Japanese consortium study under permission of the ethical committees of the enrolled institutes based on the ethics guidelines for human genome/gene analysis research, Ministry of Education, Culture, Sports, Science and Technology Ministry of Health, Labor and Welfare Ministry of Economy, Trade and Industry. In this project, 2,000 genome samples from patients with Alzheimer's disease, 2,000 control subjects, and 200 siblings affected with Alzheimer's disease are collected and analyzed. For this purpose, it is necessary to analyze samples from accurately diagnosed Alzheimer patients and controls using standard criteria for diagnosis and neuropsychological evaluation, which have been confirmed by an evidence-based studying a Japanese population. Here, we propose criteria for the diagnosis and clinical assessment of Alzheimer's disease. This proposal consists of a definition of Alzheimer's disease based on recent advances in research, diagnostic criteria based on DSM-IV, NINCDS-ADRDA and ICD-10, exclusion criteria for other dementia disorders, routine and detailed tests for neuropsychological and laboratory evaluations, criteria for neuroimaging and biomarkers, definitive diagnostic criteria and classification of clinical subtypes.

Alzheimer Disease↗
PubMed2004

Dual mode regulation of migration by lysophosphatidic acid in human gastric cancer cells.

Lysophosphatidic acid (LPA), which interacts with at least three G protein-coupled receptors (GPCRs), LPA1/Edg-2, LPA2/Edg-4, and LPA3/Edg-7, is a lipid mediator with diverse effects on various cells. Here, we investigated the expression profiles of LPA receptors and patterns of LPA-induced migration in gastric cancer cells. Northern blot analysis revealed that various gastric cancer cells expressed variable levels of LPA1, LPA2, and LPA3 without a consistent pattern. Using a Boyden chamber assay, LPA markedly increased cell migration of LPA1-expressing cells, the effects of which were almost totally abrogated by Ki16425, an LPA antagonist against LPA1 and LPA3. In contrast, LPA by itself did not significantly induce migration in MKN28 and MKN74 cells, which exclusively expressed LPA2. However, when hepatocyte growth factor (HGF) was placed with LPA in the lower chamber, LPA induced migration of these cells in a dose-dependent manner. Immunoprecipitation analysis revealed that LPA induced transient tyrosine phosphorylation of c-Met in LPA2-expressing cells, which suggests that the transactivation of c-Met by LPA causes a cooperative migratory response with HGF to these cells. Our results indicate that LPA regulates the migration of gastric cancer cells in a receptor-specific manner and suggest that the expression pattern of LPA receptors may affect the metastatic behavior of gastric cancer.

Chemotaxis↗
PubMed2004

The neural correlates of driving performance identified using positron emission tomography.

Driving is a complex behavior involving multiple cognitive domains. To identify neural correlates of driving performance, [15O]H2O positron emission tomography was performed using a simulated driving task. Compared with the resting condition, simulated driving increased regional cerebral blood flow (rCBF) in the cerebellum, occipital, and parietal cortices. Correlations between rCBF and measurements of driving performance were evaluated during simulated driving. Interestingly, rCBF in the thalamus, midbrain, and cerebellum were positively correlated with time required to complete the course and rCBF in the posterior cingulate gyrus was positively correlated with number of crashes during the task. These brain regions may thus play roles in the maintenance of driving performance.

Adult↗
PubMed2004

Alkyl lysophosphatidic acid and fluoromethylene phosphonate analogs as metabolically-stabilized agonists for LPA receptors.

We describe an efficient method for the synthesis of alkyl lysophosphatidic acid (LPA) analogs as well as alkyl LPA mono- and difluoromethylene phosphonate analogs. Each alkyl LPA analog was evaluated for subtype-specific LPA receptor agonist activity using a cell migration assay for LPA(1) activation in cancer cells and an intracellular calcium mobilization assay for LPA(2) and LPA(3) activation. Alkyl LPAs induced pronounced cell migration activity with equivalent or higher potency than sn-1-oleoyl LPA, while the alkyl LPA fluoromethylene phosphonates proved to be less potent agonists in this assay. However, each alkyl LPA analog activated Ca(2+) release by activation of LPA(2) and LPA(3) receptors. Interestingly, the absolute configuration of the sn-2 hydroxyl group of the alkyl LPA analogs was not recognized by any of the three LPA receptors. The use of alkyl LPA analogs further expands the scope of structure-activity studies, which will better define LPA-LPA receptor interactions.

Animals↗
PubMed2004

Anti-apoptotic actions of the platelet-activating factor acetylhydrolase I alpha2 catalytic subunit.

Platelet-activating factor (PAF) is an important mediator of cell loss following diverse pathophysiological challenges, but the manner in which PAF transduces death is not clear. Both PAF receptor-dependent and -independent pathways are implicated. In this study, we show that extracellular PAF can be internalized through PAF receptor-independent mechanisms and can initiate caspase-3-dependent apoptosis when cytosolic concentrations are elevated by approximately 15 pM/cell for 60 min. Reducing cytosolic PAF to less than 10 pM/cell terminates apoptotic signaling. By pharmacological inhibition of PAF acetylhydrolase I and II (PAF-AH) activity and down-regulation of PAF-AH I catalytic subunits by RNA interference, we show that the PAF receptor-independent death pathway is regulated by PAF-AH I and, to a lesser extent, by PAF-AH II. Moreover, the anti-apoptotic actions of PAF-AH I are subunit-specific. PAF-AH I alpha1 regulates intracellular PAF concentrations under normal physiological conditions, but expression is not sufficient to reduce an acute rise in intracellular PAF levels. PAF-AH I alpha2 expression is induced when cells are deprived of serum or exposed to apoptogenic PAF concentrations limiting the duration of pathological cytosolic PAF accumulation. To block PAF receptor-independent death pathway, we screened a panel of PAF antagonists (CV-3988, CV-6209, BN 52021, and FR 49175). BN 52021 and FR 49175 accelerated PAF hydrolysis and inhibited PAF-mediated caspase 3 activation. Both antagonists act indirectly to promote PAF-AH I alpha2 homodimer activity by reducing PAF-AH I alpha1 expression. These findings identify PAF-AH I alpha2 as a potent anti-apoptotic protein and describe a new means of pharmacologically targeting PAF-AH I to inhibit PAF-mediated cell death.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗