Biomedical subjects

Hitoshi Okamura

Publications and source records attributed to Hitoshi Okamura.

86 records · Page 5Linked to original sources

PubMed2002

Molecular machinery of the circadian clock in mammals.

The discovery of clock genes and the general principle of their oscillation has stimulated research on biological clocks and this research has had a major impact on the field of life sciences. The mammalian circadian core oscillator is thought to be composed of an autoregulatory transcription-(post)translation-based feedback loop involving a set of clock genes. The real time monitoring of clock gene oscillation at the levels of genes, cells, tissues, and systems will clarify the issue of how the time signal is born and how it is integrated into the organismic level. Investigations of circadian systems in various organisms employ multiple methods including ethology, physiology, neuroscience, molecular biology, cell biology and genetics. The circadian system has thus become a unique example in the elucidation of the general principles of how genes control cellular, systemic and behavioral functions.

Animals↗

PubMed2002

Rev-erbalpha gene expression in the mouse brain with special emphasis on its circadian profiles in the suprachiasmatic nucleus.

Rev-erbalpha is an orphan nuclear receptor that constitutively suppresses gene transcription. In the present study, the expression of Rev-erbalpha was investigated in the mouse brain by in situ hybridization using antisense cRNA probe. Positive Rev-erbalpha mRNA signals were detected widely in the brain with the highest expression in the suprachiasmatic nucleus (SCN). In the constant dark condition, the circadian expression profiles of Rev-erbalpha m RNA in the SCN showed a peak at early daytime (CT4) and a trough at early night time (CT16). The environmental lighting condition (light-dark environmental condition and exposure in the subjective night) did not alter the expression profiles. These findings indicate that Rev-erbalpha gene is a transcription factor intimately related to the circadian clock in the SCN.

Animals↗

PubMed2002

Thymidine kinase in epithelial ovarian cancer: relationship with the other pyrimidine pathway enzymes.

TK is a pyrimidine metabolic pathway enzyme involved in salvage DNA synthesis. What roles TK may play in epithelial ovarian cancer and the relationships between TK and the other pyrimidine pathway enzymes remain unclear. We examined TK1 gene expression by RT-PCR and related it to gene expression of TS, TP and DPD in 69 samples from epithelial ovarian cancer, 8 low-malignant-potential tumors, 16 benign ovarian tumors and 34 normal ovaries. Additionally, cytosolic and serum TK activities were determined by radioenzymatic assay. TK1 gene expression, the ratio of TK1 to TS gene expression, that of TK1 to TP and that of TK1 to DPD were significantly higher in epithelial ovarian cancer than in normal ovaries. In epithelial ovarian cancer, TK1 gene expression correlated with cytosolic and serum TK activities, TS and TP gene expression and the ratio of TP to DPD gene expression. Patients with high-TK1 gene expression had a significantly poorer survival than those with low TK1 gene expression. Combined analysis demonstrated that the relative risk of cancer death for tumors with high TK1, high TS and high TP gene expression was greater than that for tumors with high TK1 gene expression alone. TK1 gene expression together with TS, TP and DPD gene expression may play important roles in influencing the malignant behavior of epithelial ovarian cancer. Combination therapy including TK inhibitor is a possible therapeutic intervention in patients with epithelial ovarian cancer.

Aged↗

PubMed2002

Nucleocytoplasmic shuttling and mCRY-dependent inhibition of ubiquitylation of the mPER2 clock protein.

The core oscillator generating circadian rhythms in eukaryotes is composed of transcription--translation-based autoregulatory feedback loops in which clock gene products negatively affect their own expression. A key step in this mechanism involves the periodic nuclear accumulation of clock proteins following their mRNA rhythms after approximately 6 h delay. Nuclear accumulation of mPER2 is promoted by mCRY proteins. Here, using COS7 cells and mCry1/mCry2 double mutant mouse embryonic fibroblasts transiently expressing GFP-tagged (mutant) mPER2, we show that the protein shuttles between nucleus and cytoplasm using functional nuclear localization and nuclear export sequences. Moreover, we provide evidence that mCRY proteins prevent ubiquitylation of mPER2 and subsequent degradation of the latter protein by the proteasome system. Interestingly, mPER2 in turn prevents ubiquitylation and degradation of mCRY proteins. On the basis of these data we propose a model in which shuttling mPER2 is ubiquitylated and degraded by the proteasome unless it is retained in the nucleus by mCRY proteins.

3T3 Cells↗

PubMed2002

Rhythmic expression of ROR beta mRNA in the mice suprachiasmatic nucleus.

The expression of the brain rich orphan nuclear receptor ROR beta (retinoid-related orphan receptor beta) was investigated in the mouse brain by in situ hybridization using antisense cRNA probe. Positive ROR beta mRNA signals were detected in various parts of the brain with high expression in the suprachiasmatic nucleus (SCN). In the SCN, ROR beta mRNA signals showed a peak at early daytime (ZT/CT4) and a trough at early nighttime (ZT/CT16) in both light-dark and constant dark conditions. Light exposure at subjective night did not alter the expression level. These findings suggest that ROR beta is a new member of a transcription factor possibly related to the circadian pacemaking system.

Animals↗

PubMed2002

Hypoxia-inducible factor 1 alpha (HIF-1 alpha) gene expression in human ovarian carcinoma.

Hypoxia-inducible factor 1 alpha (HIF-1 alpha) that regulates genes involved in response to hypoxia and promotes neo-angiogenesis, is a transcriptional factor for vascular endothelial cell growth factor (VEGF). The aim of this study was to examine the expression of HIF-1 alpha and VEGF gene expressions and their relation to angiogenesis, clinicopathologic variables and survival in the patient with human ovarian carcinoma. We retrospectively analyzed HIF-1 alpha and VEGF gene expression levels using reverse transcriptase polymerase chain reaction (RT-PCR) in 60 ovarian carcinomas. Intratumoral microvessel density (IMD) was assessed by immunostaining endothelial cells, using anti-CD 31 antibody in frozen sections. The relationships between the expression level of these genes, IMD and clinicopathologic variables were evaluated by Student's t-test and chi-square tests. Survival analysis was performed by Kaplan-Meier curves. HIF-1 alpha or VEGF gene expression level was independent of age, clinical stage and histological subtype besides grade of tumor. There was no relationship between HIF-1 alpha or VEGF gene expression level and IMD in all carcinomas (R=0.118 and 0.224, respectively). In addition, a weak association between HIF-1 alpha and VEGF gene expression level was observed (R=0.300, P=0.020). The association between VEGF gene expression and IMD was observed (R=0.501, P=0.016). However, no association between IMD and HIF-1 alpha gene expression was observed. Further, both HIF-1 alpha and VEGF gene expression levels had no effect on survival in the patient with ovarian carcinoma. These results suggest that VEGF upregulated by HIF-1 alpha gene may be involved in angiogenesis of some type of ovarian carcinoma, but the expression levels of both genes have no effect on survival in the patients with ovarian carcinoma.

Adult↗

PubMed2002

Opposing actions of neuropeptide Y and light on the expression of circadian clock genes in the mouse suprachiasmatic nuclei.

The circadian clockwork of the hypothalamic suprachiasmatic nuclei (SCN) is synchronized by light and by nonphotic cues. The core timing mechanism is cell-autonomous, based on an autoregulatory transcriptional/translational feedback loop of circadian genes and their products. This study investigated the effects of neuropeptide Y (NPY), a potent nonphotic resetting cue, and its interaction with light in regulating clock gene expression in the SCN in vivo. Injection of NPY adjacent to the SCN and transfer to darkness 7 h before scheduled lights out, shifted the circadian activity-rest cycle. Exposure to light for 1 h immediately after NPY infusion blocked this behavioural response. NPY-induced shifts were accompanied by suppression of both mPer1 and mPer2 mRNA in the SCN, assessed 3 h after infusion. mPer mRNAs were not altered 1 h after infusion. Levels of mClock mRNA or mCLOCK immunoreactivity in the SCN were not affected by NPY at either time point. In parallel to the behavioural response, the NPY-induced suppression of mPer genes in the SCN was attenuated when a light pulse was delivered immediately after the infusion. These results identify mPer1 and mPer2 as molecular targets for both photic and nonphotic (NPY-induced) resetting of the clockwork, and support a synthetic model of circadian entrainment based upon convergent up- and downregulation of mPer expression.

Animals↗

PubMed2002

Restoration of circadian behavioural rhythms in a period null Drosophila mutant (per01) by mammalian period homologues mPer1 and mPer2.

BACKGROUND: Recent molecular studies suggest that mammals and Drosophila utilize similar components to generate circadian (approximately equal to 24 h) rhythms. The first identified circadian clock gene, the period (per) gene, is indispensable for behavioural rhythms in Drosophila and is represented in mammals by three orthologues, the relative roles of which are not known. In this study, we investigated the functional conservation of per by introducing the mouse mPer1 and mPer2 genes, driven by the Drosophila timeless (tim) promoter, into Drosophila melanogaster. RESULTS: Behavioural assays showed that both mPer constructs restored rhythms in per(01) flies that are otherwise arrhythmic due to a lack of endogenous per protein (PER). However, the rhythms restored by mPer2 were generally stronger and differed in periodicity from those restored by mPer1. In rhythmic transgenic flies, mPER proteins were expressed in lateral neurones and/or many cells in optic lobe. In addition, cell culture experiments indicated that the Drosophila PER partner, TIM, can form a complex with each of these two mammalian proteins. CONCLUSIONS: This study demonstrates that both mPer1 and mPer2 can function as clock components, and has implications for a functional analysis of the different per genes.

Animals↗

PubMed2002

Circadian rhythm of aromatic L-amino acid decarboxylase in the rat suprachiasmatic nucleus: gene expression and decarboxylating activity in clock oscillating cells.

BACKGROUND: Aromatic L-amino acid decarboxylase (AADC) is the enzyme responsible for the decarboxylation step in both the catecholamine and indoleamine synthetic pathways. In the brain, however, a group of AADC containing neurones is found outside the classical monoaminergic cell groups. Since such non-monoaminergic AADC is expressed abundantly in the suprachiasmatic nucleus (SCN), the mammalian circadian centre, we characterized the role of AADC in circadian oscillation. RESULTS: AADC gene expression was observed in neurones of the dorsomedial subdivision of the SCN and its dorsal continuant in the anterior hypothalamic area. These AADC neurones could uptake exogenously applied L-DOPA and formed dopamine. AADC was co-expressed with vasopressin and the clock gene Per1 in the neurones of the SCN. Circadian gene expression of AADC was observed with a peak at subjective day and a trough at subjective night. The circadian rhythm of AADC enzyme activity in the SCN reflects the expression of the gene. CONCLUSIONS: Non-monoaminergic AADC in the SCN is expressed in clock oscillating cells, and the decarboxylating activity of master clock cells are under the control of the circadian rhythm.

Animals↗

PubMed2002

Gradients in the circadian expression of Per1 and Per2 genes in the rat suprachiasmatic nucleus.

The suprachiasmatic nucleus (SCN) is the mammalian circadian pacemaker, which consists of thousands of oscillator cells. It is believed that the circadian oscillation in each cell is generated by the transcription/(post)-translation feedback loop of a set of clock genes. However, little is known about how these oscillator cells are organized to produce the robust circadian rhythms in the SCN. In the present study, we examined the expression of the clock genes Per1 and Per2 paying particular attention to the topographic compartmentalization of the SCN. In the rat SCN, the dorsomedial (SCNDM) and ventrolateral (SCNVL) compartments are clearly delineated by chemical characteristics of neurons and neuronal afferents. In the SCNDM, Per1 mRNA was initially expressed at the most dorsomedial region along the third ventricle (SCNDMPV, periventricular part of the dorsomedial compartment of the SCN) at CT0, and then spread laterally to the central dorsomedial region (SCNDMCe, central part of the dorsomedial compartment of the SCN), reaching peaks at subjective day and troughs at subjective night. In contrast, in the SCNVL, Per1 expression showed a weak, two-peak pattern in one circadian cycle. Per2 expression was also robust in the SCN, showing very similar circadian profiles among these three subdivisions with a slightly earlier phase in SCNDMPV than that in SCNDMCe. We also investigated the Per1 and Per2 expression in response to a light exposure at early subjective night. The light pulse induced both Per1 and Per2 expression, which was restricted in the SCNVL neurons. The present findings suggest that the phase and amplitude of the circadian expression of clock genes are not uniform, and there are topographic neuron groups that have different properties in the SCN.

Animals↗

PubMed2002

Clinical factors associated with suicidality in cancer patients.

BACKGROUND: Previous epidemiological studies have indicated that the risk of suicide in cancer patients is higher than that of the general population. In addition, euthanasia and physician-assisted suicide (PAS) have recently become controversial medical, ethical and legal issues all over the world. Although suicide in cancer patients and appropriate management of cancer patients with suicidality are critical issues in clinical oncology practice, there have been very few studies to understand suicidality in cancer patients. The purpose of this study was to explore the clinical factors associated with suicidality in Japanese patients with cancer. METHODS: We investigated the clinical factors associated with suicidality in cancer patients by analyzing the consultation data of patients referred to the Psychiatry Division, National Cancer Centre Hospital and Hospital East, Japan. RESULTS: Of 1713 psychiatric referrals, 62 (3.6%) were related to suicidality, including 44 cases with suicidal ideation, 10 suicide attempts and eight cases who had requested euthanasia and/or continuous sedation. Most of the patients suffered from physical distress and/or psychiatric disorders. The results of a multivariate analysis comparing cancer patients with a psychiatric referral related to suicidality and those referred for other reasons indicated that impaired physical functioning and major depression were significant associated factors. CONCLUSIONS: Our findings suggest that early detection and appropriate management of major depression and comprehensive care improving physical functioning may help to prevent suicide and manage suicidality in Japanese cancer patients.

Adult↗

PubMed2002

A diminished intrapartum amniotic fluid index is a predictive marker of possible adverse neonatal outcome when associated with prolonged labor.

OBJECTIVE: To determine whether a diminished intrapartum amniotic fluid volume represents a risk of adverse neonatal outcome when it occurs in conjunction with prolonged labor. METHODS: The intrapartum amniotic fluid index (iAFI) was measured in 242 parturients over 35 weeks of gestation during 1st-stage labor, and the umbilical artery blood gas was analyzed at delivery. The subjects were divided into group A (n = 99), having a diminished amniotic fluid volume (iAFI < or = 8.0 cm) and group B (n = 143), having a normal amniotic fluid volume (iAFI 8.1-20.0 cm), and selected antenatal, delivery, and neonatal variables were compared. In addition, the two groups were subdivided according to the duration of labor. Statistical analysis was performed using independent Student's t test, Mann-Whitney U test, chi-square analysis, and Fisher's exact test where appropriate. p < 0.05 was considered significant. RESULTS: The patient characteristics and pregnancy outcomes were similar in groups A and B, as were the incidences of an umbilical artery blood pH <7.20 and/or an Apgar score <7 (group A 9.5%, group B 10.1%). In group A, however, the incidence of an adverse neonatal outcome was 23.5% in cases in whom the duration of labor was longer than 8 h which was significantly higher than in cases in whom the duration of labor was 8 h or less (2.8%; p < 0.01). In group B, the incidence of an adverse neonatal outcome was similar in the two subgroups. CONCLUSIONS: The risk of an adverse neonatal outcome is higher in patients with diminished amniotic fluid volume if labor is prolonged. Consequently, determination of the iAFI could be a useful admission test.

Adult↗

PubMedDate not supplied

Study on effects of life review activities on the quality of life of the elderly: a randomized controlled trial.

BACKGROUND: The objective of this study was to evaluate the mid-term efficacy of life review activities on the quality of life (QOL) of the elderly by conducting a randomized controlled trial, and to identify the factors that should be taken into consideration when conducting life review activities. METHODS: Written consent was obtained from 80 of the 97 eligible elderly persons. After randomly assigning them to two groups, an intervention group and a control group, group life review activities were conducted in the intervention group and discussion activities about health were conducted in the control group. In both the intervention group and the control group, life satisfaction, self-esteem, depression, and hopelessness were evaluated using self-rating scales at three points: at baseline, immediately after completion of the 8 weeks of sessions, and 3 months after completion of the intervention. RESULTS: Repeated measures analysis of covariance showed significant differences between the two groups in the changes in scores for depression (p = 0.04) and hopelessness (p = 0.04). Regarding the factors that were associated with depression and hopelessness, 3 months after completion of the intervention, depression and hopelessness of a more severe nature at baseline and having greater unresolved conflicts in the past were extracted by multiple regression analysis. CONCLUSIONS: The results suggested that group life review activities have a role in assisting the developmental stage of old age and supporting mental health, and have mid- to long-term effectiveness in maintaining and improving the QOL of the elderly.

Aged↗

PubMedDate not supplied

Serum endostatin levels in patients with epithelial ovarian cancer.

OBJECTIVE: Endostatin, a 20-kDa C-terminal fragment of collagen XVIII, specifically inhibits endothelial proliferation and potently inhibits angiogenesis and tumor growth. The aim of this study was to assess the prognostic potentials of serum endostatin levels in epithelial ovarian cancer. MATERIALS AND METHODS: The preoperative serum levels of endostatin in 61 cases of epithelial ovarian cancer (29 serous, 13 mucinous, 13 endometrioid, 5 clear cell and 1 Brenner cell) were analyzed using a competitive enzyme immunoassay. With regard to staging, 23 cases had stage I disease, 6 had stage II disease, 28 had stage III disease and 4 had stage IV disease. RESULTS: Serum levels were compared with levels from 22 age-matched healthy volunteer blood donors. The median serum levels were 18.5 ng/ml (range, 6.3-50.3 ng/ml) in patients with epithelial ovarian cancer and 18.4 ng/ml (range, 8.4-27.0 ng/ml) in controls. No significant difference was noted between the two groups. No clinicopathological features (e.g., patients' age at diagnosis, stage of disease, histological subtype and grade) were significantly associated with serum endostatin levels. Survival data were available for all patients. Multivariate Cox regression analysis revealed that FIGO stage III-IV (p = 0.015) and serum endostatin levels (> 2 standard deviations above the control mean; 27.7 ng/ml) (p = 0.035) are independent prognostic factors. CONCLUSION: Elevated serum levels of this endogenous inhibitor of angiogenesis may be a pertinent prognostic indicator for patients with epithelial ovarian cancer. It is anticipated that this finding may aid the development of a new therapeutic strategy for epithelial ovarian cancer.

Adult↗