Biomedical subjects

Masaaki Tanaka

Publications and source records attributed to Masaaki Tanaka.

At least 19 recordsLinked to original sources

PubMed2006

Decrease of hepatic delta-aminolevulinate dehydratase activity in an animal model of fatigue.

Fatigue can be defined physiologically as inability to maintain the expected power output. At present, no standard of fatigue are yet available. In order to find biomarkers of fatigue, we investigated the level of delta-aminolevulinic acid (ALA), the first intermediate metabolite in the heme biosynthetic pathway, in the plasma and urine of an animal model of fatigue. To prepare fatigued animals, we kept rats for 5 days in a cage filled with water to a height of 1.5 cm. As a result, the plasma and urinary ALA levels were increased in the fatigued animals as compared with those in the control animals. One day after the rats had been returned to their normal cages, these increased levels were restored to the control ones. We also examined the activity of the enzyme ALA dehydratase (ALAD), which is the second enzyme in the heme biosynthetic pathway, and ALAD gene expression during the fatigue and its recovery sessions. The ALAD activity, as well as its gene expression, in the liver of the fatigued animals was decreased as compared with those of the control animals. Both activity and gene expression of ALAD were recovered to their respective control levels after the rats had been allowed to rest in their normal cages for 1 day. Furthermore, the activity of ALA synthase (ALAS), the rate-limiting enzyme in the heme biosynthesis, in the liver was increased after the fatigue session for 5 days. Although this level of increase in the plasma concentration of ALA may not induce fatigue, increase in plasma and urinary ALA levels can be biomarkers of fatigue.

5-Aminolevulinate Synthetase↗

PubMed2006

Reduced responsiveness is an essential feature of chronic fatigue syndrome: a fMRI study.

BACKGROUND: Although the neural mechanism of chronic fatigue syndrome has been investigated by a number of researchers, it remains poorly understood. METHODS: Using functional magnetic resonance imaging, we studied brain responsiveness in 6 male chronic fatigue syndrome patients and in 7 age-matched male healthy volunteers. Responsiveness of auditory cortices to transient, short-lived, noise reduction was measured while subjects performed a fatigue-inducing continual visual search task. RESULTS: Responsiveness of the task-dependent brain regions was decreased after the fatigue-inducing task in the normal and chronic fatigue syndrome subjects and the decrement of the responsiveness was equivalent between the 2 groups. In contrast, during the fatigue-inducing period, although responsiveness of auditory cortices remained constant in the normal subjects, it was attenuated in the chronic fatigue syndrome patients. In addition, the rate of this attenuation was positively correlated with the subjective sensation of fatigue as measured using a fatigue visual analogue scale, immediately before the magnetic resonance imaging session. CONCLUSION: Chronic fatigue syndrome may be characterised by attenuation of the responsiveness to stimuli not directly related to the fatigue-inducing task.

Adult↗

PubMed2005

MicroPET detection of enhanced 18F-FDG utilization by PKA inhibitor in awake rat brain.

To obtain PET imaging of glucose metabolism in the brains of conscious rats, a method of rat head fixation was developed. PET measurement with microPET was performed for 60 min after 18F-FDG injection. Significant enhancement of glucose utilization in the right striatum was observed with infusion of Rp-adenosine-3,5-cyclic phosphorothioate triethylamine (Rp-cAMPS). FDG uptake increments were also seen in the ipsilateral frontal cortex and thalamus. As initial FDG uptake in the brain was not significantly altered by Rp-cAMPS, increased glucose metabolism might be due to an increase in the phosphorylation rate by hexokinase rather than the delivery process from plasma to the brain. In contrast to awake rats, the effect of Rp-cAMPS was abolished by anesthesia using chloral hydrate, indicating that neuronal activity has an important role in short term regulation of hexokinase activity through the cAMP/PKA system in the brain. These results strongly demonstrated the value of measuring glucose utilization in the brains of conscious rats.

Anesthetics↗

PubMed2005

Efficient inhibition of human telomerase reverse transcriptase expression by RNA interference sensitizes cancer cells to ionizing radiation and chemotherapy.

Telomerase activation plays critical roles in tumor growth and progression in part through the maintenance of telomere structure. Indeed, the ubiquitous expression of telomerase in human cancers makes telomerase a promising target for cancer therapy. Genetic, pharmacologic, and antisense methods to inhibit telomerase have been described; however, in most cases, cancer cell death was observed only after many cell divisions. Here, using retroviral delivery of small interfering RNAs (siRNAs) specific for the human telomerase reverse transcriptase (hTERT), we successfully inhibited telomerase activity in cervical cancer cell lines. Cells lacking hTERT expression exhibited significantly decreased telomerase activity and showed shortened telomeres and telomeric 3' overhangs with passage. These cells entered replicative senescence after a considerable number of cell divisions. Notably, the proliferative rate of these cells was significantly impaired, compared with control cells with telomerase activity, even in low-passage cells (population doubling 5). Likewise, colony-forming ability and tumorigenicity in mice were attenuated in low-passage cells lacking hTERT. We further examined the effects of chemotherapy and ionizing radiation on cells in which hTERT expression was suppressed. Cells lacking hTERT showed a significantly increased sensitivity, compared with control cells, to ionizing radiation or chemotherapeutic agents that induce DNA double- strand breaks, such as topoisomerase inhibitors or bleomycin. These findings suggest that an siRNA-based strategy can be applied to the development of novel telomerase inhibitors, the antitumor effects of which may be enhanced in combination with ionizing radiation and chemotherapy.

Animals↗

PubMed2005

Altered expression of neprilysin family members in the pituitary gland of sleep-disturbed rats, an animal model of severe fatigue.

Alterations of the expression of some peptidases in the pituitary gland of a fatigued rat model were identified. Rats were kept in a cage filled with water to a height of 1.5 cm to disturb deep sleep. After 24-h sleep disturbance, expression of neutral endopeptidase 24.11 (neprilysin) mRNA was increased in the intermediate lobe of the pituitary gland, whereas the mRNA expression of another family member, damage-induced neuronal endopeptidase, which is normally expressed in a subgroup of anterior pituitary cells, was significantly suppressed. These alterations were demonstrated by RT-PCR, northern blotting and in situ hybridization. Other family members, such as neprilysin 2 and endothelin converting enzyme-1, did not show any change in mRNA expression. An increase of neprilysin mRNA expression was not seen in any other tissues of the sleep-disturbed rats. The enzymatic activity of neprilysin was also increased in the pituitary. The augmentation of neprilysin expression and activity was prolonged as long as the sleep disturbance continued (up to 5 days), and returned to the basal level when rats were allowed to sleep freely. These results suggest that peptide processing and degradation in the pituitary may be an influential factor in fatigued states such as sleep disturbance.

Adrenocorticotropic Hormone↗

PubMed2005

Pharmacokinetics of paclitaxel in ovarian cancer patients and genetic polymorphisms of CYP2C8, CYP3A4, and MDR1.

Interindividual differences in the pharmacokinetics of paclitaxel and its metabolites in Japanese ovarian cancer patients were investigated in relation to genetic polymorphisms of the CYP2C8, CYP3A4, and MDR1 genes. The area under the concentration-time curve (AUC) ratios of paclitaxel/6alpha-hydroxypaclitaxel and paclitaxel/3 -p-hydroxypaclitaxel calculated as the metabolic index of CYP2C8 and CYP3A4 showed 13- and 12-fold interindividual variations, respectively. No patient had any CYP2C8 variants, while 2 patients were heterozygotes of CYP3A4*16. For the MDR1 gene, the frequencies of -129C, 1236C, 2677T, 2677A, and 3435T alleles were 2.2%, 8.7%, 56.5%, 4.4%, and 52.2%, respectively. Subjects possessing the 3435T allele had a significantly (P < .05) higher AUC of 3'- p-hydroxypaclitaxel compared to those possessing the 3435C allele. Leukocytopenia was significantly (P < .05) related to the AUC of paclitaxel. Genotyping of the CYP2C8, CYP3A4, and MDR1 genes might not be essential to predict adverse effects of paclitaxel in Japanese patients, although an allelic variant of MDR1 may functionally affect the pharmacokinetics of its metabolite.

Area Under Curve↗

PubMed2005

Phenotypic diversity in patients with craniosynostoses unrelated to Apert syndrome: the role of fibroblast growth factor receptor gene mutations.

OBJECT: The goal of this study was to elucidate the genotype-phenotype relationship in syndromic craniosynostoses by analyzing the mutations of the fibroblast growth factor receptor (FGFR) gene and its clinical manifestations in patients, particularly those in atypical cases. METHODS: Twenty patients with craniosynostoses unrelated to Apert syndrome were enrolled in this study. The phenotypes indicated the following syndromes: 12 patients with unrelated Crouzon syndrome, including nine sporadic and three familial cases; two with sporadic Pfeiffer syndrome; and one with Antley-Bixler syndrome. The Crouzon phenotype was subdivided into three clinical forms: regular, top, and bottom ones. Two patients who demonstrated craniofacial anomalies and bilateral elbow joint contractures were categorized as having an unspecified craniosynostosis. Three cases of unclassifiable cloverleaf skull malformation were also analyzed. Fourteen mutations of the FGFR2 gene were identified in these patients; seven of the 10 cysteine-related mutations were substitutions of codon 342 in the third immunoglobulin-like domain of this gene. The phenotypes of these seven cases were three of regular Crouzon, two of unspecified craniosynostosis, and one each of top Crouzon and unclassifiable cloverleaf skull malformation. In addition, four of the seven patients were found to have the same genotype (Cys342Arg). The phenotypes of these patients, however, were quite variable, ranging from regular Crouzon to unclassifiable cloverleaf skull malformation. CONCLUSIONS: The phenotypes of patients with craniosynostoses unrelated to Apert syndrome proved quite variable, even in cases in which patients demonstrated the same genotype. In view of the phenotypic diversity evident in cases in which the same mutation in the FGFR2 gene is present, it is possible that other disease-modifying genetic factors exist to control the abnormal gain-of-function that accompanies FGFR signaling.

Adolescent↗

PubMed2004

Mechanisms underlying fatigue: a voxel-based morphometric study of chronic fatigue syndrome.

BACKGROUND: Fatigue is a crucial sensation that triggers rest, yet its underlying neuronal mechanisms remain unclear. Intense long-term fatigue is a symptom of chronic fatigue syndrome, which is used as a model to study the mechanisms underlying fatigue. METHODS: Using magnetic resonance imaging, we conducted voxel-based morphometry of 16 patients and 49 age-matched healthy control subjects. RESULTS: We found that patients with chronic fatigue syndrome had reduced gray-matter volume in the bilateral prefrontal cortex. Within these areas, the volume reduction in the right prefrontal cortex paralleled the severity of the fatigue of the subjects. CONCLUSION: These results are consistent with previous reports of an abnormal distribution of acetyl-L-carnitine uptake, which is one of the biochemical markers of chronic fatigue syndrome, in the prefrontal cortex. Thus, the prefrontal cortex might be an important element of the neural system that regulates sensations of fatigue.

Adult↗

PubMed2004

HIF-1-mediated activation of telomerase in cervical cancer cells.

Hypoxia-inducible factor 1 (HIF-1) is a key regulator of O(2) homeostasis, which regulates the expression of several genes linked to angiogenesis and energy metabolism. Tumor hypoxia has been shown to be associated with poor prognosis in a variety of tumors, and HIF-1 induced by hypoxia plays pivotal roles in tumor progression. The presence of putative HIF-1-binding sites on the promoter of human telomerase reverse transcriptase gene (hTERT) prompted us to examine the involvement of HIF-1 in the regulation of hTERT and telomerase in tumor hypoxia. The telomeric repeat amplification protocol (TRAP) assay revealed that hypoxia activated telomerase in cervical cancer ME180 cells, with peak induction at 24-48 h of hypoxia. Notably, hTERT mRNA expression was upregulated at 6-12 h of hypoxia, concordant with the elevation of HIF-1 protein levels at 6 h. hTERT protein levels were subsequently upregulated at 24 h and later. Luciferase assays using reporter plasmids containing hTERT core promoter revealed that hTERT transcription was significantly activated in hypoxia and by HIF-1 overexpression, and that the two putative binding sites within the core promoter are responsible for this activation. Chromatin immunoprecipitation assay identified the specific binding of HIF-1 to these sites (competing with c-Myc), which was enhanced in hypoxia. The present findings suggest that hypoxia activates telomerase via transcriptional activation of hTERT, and that HIF-1 plays a critical role as a transcription factor. They also suggest the existence of novel mechanisms of telomerase activation in cancers, and have implications for the molecular basis of hypoxia-induced tumor progression and HIF-1-based cancer gene therapy.

DNA-Binding Proteins↗

PubMed2004

Role of lactate in the brain energy metabolism: revealed by Bioradiography.

To elucidate the role of lactate in the brain, we used a novel method, 'Bioradiography', in which the dynamic process could be followed in living slices by use of positron-emitter-labeled compounds and imaging plates. We studied the incorporation of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) into rat brain slices incubated in oxygenated Krebs-Ringer solution. Under the glucose-free condition, [18F]FDG uptake rate in the cerebral cortex decreased with time and plateaued within 350 min but the addition of 5 mM lactate made the [18F]FDG uptake linear. When an inhibitor of the lactate transporter, 0.5 mM alpha-cyano-4-hydroxycinnamate (4-CIN) was applied to the glucose-free solution, the uptake rate decreased. Under the normal glucose condition, [18F]FDG uptake linearly increased for 6 h, but when 10 mM lactate was applied, the uptake rate decreased. In contrast, when 0.5 mM 4-CIN was applied to the normal glucose solution, [18F]FDG uptake rate increased. These results suggest that exogenous and endogenous lactate can substitute for glucose in the brain.

Animals↗

PubMed2004

hTERT-promoter-based tumor-specific expression of MCP-1 effectively sensitizes cervical cancer cells to a low dose of cisplatin.

Cervical cancers at advanced stages or with recurrent status are mainly treated by platinum-based chemotherapy, such as cisplatin. However, a novel strategy to reduce the minimally effective dose is required to prevent severe adverse effects that limit the effectiveness of the treatment. Monocyte chemoattractant protein-1 (MCP-1) is a subtype of chemokines that can promote monocyte/macrophage infiltration and enhance their phagocytosis at not only sites of inflammatory lesions but also of tumors. The present study applies MCP-1-based gene therapy to treat cervical cancers. To achieve tumor-specific expression of MCP-1, retroviral expression vector was constructed using the human telomerase reverse transcriptase gene (hTERT) promoter. Retroviral expression of MCP-1 into cervical cancer ME180 cells did not affect their proliferation either in vitro or in vivo. However, when combined with a suboptimal low dose of cisplatin, tumor formation was obviously reduced in clones transduced with MCP-1, but not in control clones. Histological examination revealed that a substantial number of macrophages infiltrated the tumor sites of MCP-1-transduced cells, but not of controls. These findings suggest that MCP-1 expression sensitizes cervical cancer cells to an otherwise ineffective low dose of cisplatin, possibly by inducing the migration of macrophages to eradicate tumor cells. This system may be a novel strategy for chemotherapy combined with immunogene therapy against otherwise intractable cervical cancers.

Animals↗

PubMed2004

Mapping Japanese medical terms to UMLS Metathesaurus.

This paper introduces and reports the results for a project to map Japanese medical terms to the UMLS Metathesaurus. The "Thesaurus for Medical and Health related Terms version 5" published in 2003 by the Japan Medical Abstracts Society and UMLS version 2002AC provided by NLM were used in this study. The goal was to judge the validity of the correlation between the Japanese and English terms that belong to the same MeSH concept. Fifteen medicine, nursing, and library science professionals, excluding JAMAS, used a custom designed Web interface to perform this task. About 10% of the concepts were judged as invalid, and the reasoning behind these failures were analyzed. Experience from this project can be used to estimate the manpower required to revise the Japanese thesaurus after future revisions to UMLS or MeSH.

Internet↗

PubMed2003

Recovery from fatigue: changes in local brain 2-[18F]fluoro-2-deoxy-D-glucose utilization measured by autoradiography and in brain monoamine levels of rat.

We recently established an animal model of fatigue in which rats were kept in a cage filled with water to a height of 1.5 cm for 5 days. In this way, after the fatigue session, they were returned to their home cage. Rats resting for 15 min or 2 h showed reduced 2-[18F]fluoro-2-deoxy-D-glucose uptake in their brain. Rats resting for 1 h showed a significantly increased ratio of 5-hydroxyindoleacetic acid/5-hydroxytryptamine, an index of serotonin turnover, in the frontal cortex, hippocampus, and cerebellum, and the ratio of [3,4-dihydroxyphenylacetic acid+homovanillic acid]/dopamine, an index of dopamine turnover, tended to be increased as compared with the control. These data suggest that improvement of glucose uptake and increased serotonergic and dopaminergic neuronal activities are associated with recovery from central fatigue.

Animals↗

PubMed2003

Establishment and assessment of a rat model of fatigue.

To establish an animal model of fatigue, we kept rats in a cage filled with water to a height of 1.5 cm. We selected a weight-loaded forced swimming test for evaluation of the extent of fatigue. Animals kept in the wet cage for 5 days showed a reduction in 2-[18F]fluoro-2-deoxy-D-glucose uptake into their brain. The session for 1 day showed significantly increased 5-hydroxyindoleacetic acid (5-HIAA)/5-hydroxytryptamine (5-HT) and [3,4-dihydroxyphenyl-acetic acid (DOPAC)+homovanillic acid (HVA)]/dopamine (DA) ratios in all brain regions, but the session for 5 days showed the restoration of the 5-HIAA/5-HT ratio in the hippocampus and hypothalamus and in the (DOPAC+HVA)/DA ratio in the striatum and hypothalamus. Our data suggest that decreased glucose uptake and insufficient serotonin and dopamine turnover introduced by deprivation of rest were correlated with central fatigue.

Animals↗

PubMed2003

Role of acetyl-L-carnitine in the brain: revealed by Bioradiography.

To elucidate the role of acetyl-L-carnitine in the brain, we used a novel method, 'Bioradiography,' in which the dynamic process could be followed in living slices by use of positron-emitter labeled compounds and imaging plates. We studied the incorporation of 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) into rat brain slices incubated in oxygenated Krebs-Ringer solution. Under the glucose-free condition, [18F]FDG uptake rate decreased with time and plateaued within 350 min in the cerebral cortex and cerebellum, and the addition of 1 or 5mM acetyl-L-carnitine did not alter the [18F]FDG uptake rate. When a glutaminase inhibitor, 0.5mM 6-diazo-5-oxo-L-norleucine (DON), was added under the normal glucose condition, [18F]FDG uptake rate decreased. Acetyl-L-carnitine (1mM), which decreased [18F]FDG uptake rate, reversed this DON-induced decrease in [18F]FDG uptake rate in the cerebral cortex. These results suggest that acetyl-L-carnitine can be used for the production of releasable glutamate rather than as an energy source in the brain.

Acetylcarnitine↗

PubMed2003

Frequent hypermethylation of MLH1 promoter in normal endometrium of patients with endometrial cancers.

Silencing of the MLH1 gene by promoter hypermethylation is the mechanism underlying the microsatellite instability (MSI) phenotype in endometrial cancers. However, the profile of CpG methylation in a wide range of MLH1 promoters in endometrial cancers and in the normal endometrium is largely unknown. The present study investigates the region 700 bp upstream of MLH1 covering 48 CpG sites using bisulfite sequencing. Methylation status was classified as full (over 80% of CpGs are methylated), partial (10-80%) or nonmethylation (less than 10%). Of 56 endometrioid endometrial cancers, 16 (29%) were fully methylated, 14 (25%) were partially methylated and 26 (46%) were not methylated. Analyses of MLH1 by immunohistochemical means and of MSI revealed that the degree, rather than region-specific methylation of CpG islands is critical for decreased MLH1 expression and the MSI phenotype. Among 12 patients with methylated cancers, five (42%) patients contained methylated promoters in their normal endometria with profiles similar to those of cancer lesions, and these were associated with the MSI phenotype. In contrast, only one of 31 (3%) normal endometria from patients without endometrial malignancies harbored methylated promoters. These findings suggest that hypermethylation of the MLH1 promoter is frequent in the histologically normal endometrium adjacent to cancers, supporting the notion that hypermethylation of mismatch repair genes is the initial step that triggers various genetic events in endometrial carcinogenesis.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Assessment of microPET performance in analyzing the rat brain under different types of anesthesia: comparison between quantitative data obtained with microPET and ex vivo autoradiography.

MicroPET (positron emission tomography) has been implemented for use in experiments with small animals. However, the quantification and optimal conditions for scanning are not established yet. The aim of this study was to compare the results obtained by microPET with those by ex vivo autoradiography of rat brain slices, based on the 2-[18F]fluoro-2-deoxy-D-glucose (FDG) method, and to establish the optimal conditions for scanning. As an example, we examined glucose metabolism in the rat brain under 6 types of anesthesia and in the conscious state. The scanning conditions for the rat brain were (1) use of a 4-mm-thick leaden jacket, (2) an energy window of 350-650 keV, and (3) a coincidence time window of 6 ns. Under these conditions, the quantitative ROI data from microPET showed a good correlation with the corresponding ROI data from FDG autoradiography in the animal study (r2=0.81). With our protocol, when anesthesia was started 40 min after the FDG injection, the glucose metabolism was almost the same as that in the conscious rat brain.

Algorithms↗

PubMed2003

Significance of immunological detection of human telomerase reverse transcriptase: re-evaluation of expression and localization of human telomerase reverse transcriptase.

Human telomerase reverse transcriptase (hTERT) is a catalytic subunit of telomerase and is a potentially useful diagnostic marker for cancers. There have been few studies in which immunological detection of hTERT has been attempted and its subcellular localization has not been precisely defined. In the present study, we re-evaluated expression and localization of hTERT in cancer and normal cells using a newly developed antibody. Immunohistochemistry revealed that hTERT is expressed in approximately 80% of gynecological cancers, but some premalignant lesions exhibited weak expression of hTERT. Interestingly, not only nuclei but also cytoplasm of cancer cells were positive for hTERT staining. This finding was supported by the results of Western blot analysis of cell lines, in which both nuclear and cytoplasmic extracts exhibited significant hTERT bands. Cytoplasmic hTERT in cancer cells may be functional because the telomeric repeat amplification protocol assay of cytoplasmic extracts showed high levels of telomerase activity. Unexpectedly, not all normal primary cells and telomerase-negative cancer cell lines lacked hTERT expression; some exhibited weak TERT signals. In Western analysis, hTERT signals did not always correlate with telomerase activity of the various cell types. These findings suggest that functional hTERT is expressed in both the nucleus and cytoplasm of cancer cells and that hTERT expression does not strictly reflect telomerase activity. Further analysis is needed to clarify the biological significance of cytoplasmic hTERT.

Blotting, Western↗