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Biomedical subjects

M Sakata

Publications and source records attributed to M Sakata.

At least 19 recordsLinked to original sources
PubMed2025

Impact of Chewing Behavior Change on Cognition and Cerebral Hemodynamics.

BACKGROUND: Impaired chewing ability is a recognized risk factor for cognitive decline in older adults, potentially due to reduced neural stimulation in cognition-related brain regions. While short-term studies have demonstrated transient increases in neural activity from chewing, the sustained cognitive and neurophysiological effects of encouraging thorough chewing habits in daily life remain unclear. OBJECTIVE: This randomized controlled trial investigated whether promoting thorough chewing during meals could improve cognitive function and cerebral hemodynamics in older adults. METHODS: Fifty participants aged 65 y or older were randomly assigned to either a 1-mo intervention group, which used a wearable device to monitor and increase chewing strokes during meals, or a control group that maintained usual chewing habits. Chewing behavior, cognitive performance (including memory and executive function via the color Stroop test), and cerebral hemodynamics in the dorsolateral prefrontal cortex (DLPFC) were measured at baseline and after 1 mo. Statistical analyses included t tests, chi-square tests, 2-way analysis of variance with post hoc tests, Pearson correlations, and generalized linear models to evaluate group differences and associations between chewing and cognitive outcomes. RESULTS: Significant time-by-group interactions were observed for memory, F(1, 48) = 6.24, P = 0.043, and hemodynamic responses in the left DLPFC, F(1, 48) = 6.19, P = 0.013. The intervention group showed increased chewing frequency (P = 0.017), improved memory performance, and reduced left DLPFC responses compared with controls. Chewing frequency was positively correlated with Stroop test scores (r = 0.53, P = 0.010) and negatively with hemodynamic changes in the left DLPFC (r = -0.30, P = 0.040). Although improvements in other cognitive outcomes and hemodynamic measures favored the intervention group, these differences did not reach statistical significance. CONCLUSIONS: Promoting intentional chewing habits for 1 mo may enhance memory-related cognitive performance and neural efficiency in the DLPFC during working memory tasks in older adults. This nonpharmacologic, low-burden strategy warrants further research with longer interventions to support cognitive health and dementia prevention. TRIAL REGISTRATION ID: UMIN000044280Knowledge Transfer Statement:This study demonstrates that promoting thorough chewing habits in older adults can improve memory and enhance neural efficiency in the brain. Encouraging intentional mastication is a simple, nonpharmacologic approach that may help maintain cognitive health and prevent dementia, providing a practical strategy for clinicians and policymakers to support healthy aging.

Humans↗
PubMed2006

Anisotropy and corotation of galactic cosmic rays.

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Journal Article↗
PubMed2006

Prevalence of premenstrual syndrome and premenstrual dysphoric disorder in Japanese women.

To investigate the prevalence and impact of premenstrual symptoms in Japanese women, we developed the PSQ "The Premenstrual Symptoms Questionnaire" for the screening of premenstrual symptoms. The PSQ translates DSM-IV criteria into a rating scale with degrees of severity. One thousand one hundred and eighty-seven Japanese women between the ages of 20 and 49 yrs, who were seen at a clinic for uterine cancer screening, were assessed regarding their premenstrual symptoms using the PSQ. As many as 95% of these women were found to suffer from premenstrual symptoms. The rates of prevalence of moderate to severe PMS and PMDD in Japanese women were 5.3 and 1.2%, respectively, which are lower than those in Western women. Only 5.3% of women with moderate to severe PMS and PMDD were treated. The results of this study suggest that race and ethnicity influence the expression of premenstrual symptoms and that the current state of medical care for Japanese women with moderate to severe PMS and PMDD is not satisfactory.

Adolescent↗
PubMed2006

Involvement of Sp-1 in the regulation of the Id-1 gene during trophoblast cell differentiation.

Id-1, a member of the helix-loop-helix transcription factor family, inhibits the differentiation of Rcho-1 cells, which were derived from rat choriocarcinoma and consist of trophoblast stem cells. Id-1 is expressed at a high level in undifferentiated trophoblast stem cells and then down-regulated during early differentiation, and is thought to be a key regulator in the trophoblast giant-cell differentiation pathway. In this study, we analyzed the signaling mechanism regulating the high expression levels of Id-1 in undifferentiated Rcho-1 cells. Promoter deletion analysis revealed that a 31-bp sequence (Box-2 region), located between -200 and -169bp in the Id-1 promoter is necessary for the promoter activity. Electrophoretic mobility shift assays and DNA affinity precipitation assays showed that Box-2-binding activity was decreased during differentiation and that Sp-1 protein bound to this sequence. The protein level of Sp-1 was decreased during the differentiation. These results suggest that the Sp-1 protein level may regulate the Box-2-binding activity and the trophoblast giant-cell differentiation.

Animals↗
PubMed2005

STAT3-mediated constitutive expression of SOCS3 in an undifferentiated rat trophoblast-like cell line.

In the trophoblast, constitutive expression of SOCS3 is important for the negative regulation of trophoblast giant cell differentiation. In this study, we analyzed the signaling pathway regulating the constitutive SOCS3 expression in undifferentiated Rcho-1 cells, which were derived from rat choriocarcinoma and consist of trophoblast stem cells that are capable of differentiating to trophoblast giant cells in vitro. PD98059, an MEK inhibitor, repressed the SOCS3 expression but AG490, a JAK2 inhibitor, did not. Promoter deletion analysis revealed that the STAT response element (SRE) in the SOCS3 promoter is necessary for the promoter activity. Overexpression of STAT3 increased the SOCS3 promoter activity, whereas expression of dominant-negative STAT3 reduced it. Constitutive STAT3 tyrosine phosphorylation that was not inhibited by either AG490 or PD98059 was demonstrated. Electrophoretic mobility shift assays showed the existence of a protein that bound to SRE and was supershifted with STAT3 antibody. This binding reaction was inhibited by neither AG490 nor PD98059. These findings imply that the ERK/MAPK pathway and STAT3 are involved in the constitutive activation of SOCS3 in undifferentiated Rcho-1 cells. Moreover, they indicate that the constitutive STAT3 tyrosine phosphorylation and the DNA binding activity of STAT3 do not depend on the ERK/MAPK or JAK kinase pathway. These results suggest that a trophoblast-specific STAT3 activation pathway is important for the regulation of giant cell differentiation.

Animals↗
PubMed2005

Distribution and toxicity of mercury in rats after oral administration of mercury-contaminated whale red meat marketed for human consumption.

Toothed-whales and dolphins have been hunted for human consumption in Japan, and their muscles (red meats) are highly contaminated with mercury (Hg). We investigated the distribution and toxicity of Hg in rats after oral administration of Hg-contaminated whale red meat marketed for human consumption in Japan. Rats were orally administered the red meat homogenate for seven consecutive days (0.5 g red meat/kg-bw/day). The red meat administered to rats contained 81microg/g of total mercury (T-Hg) and 13.4 microg/g of methyl mercury (M-Hg). This dose corresponds to the human consumption of 210 g red meat/60 kg-bw/week, exceeding by about 29 times the provisional tolerable weekly intake of M-Hg at 1.6 microg/kg-bw/week set by JECFA [JECFA, 2003. Joint FAO/WHO expert committee on food additives. 61st meeting, Rome]. Twenty-four hours after the last administration, the distribution of T-Hg in rat organs and biochemical parameters in serum were analyzed. The administration of red meat significantly elevated T-Hg concentrations in the liver, kidney, erythrocytes, cerebral cortex and medulla oblongata from the control levels but did not elevate the T-Hg concentration in serum, showing the typical distribution pattern of M-Hg, not of inorganic Hg. The administration slightly but significantly increased GTP activity and P concentration and decreased BUN concentration in serum, although no abnormalities were observed in rat body weight gain and movement during the 7 days. The occasional consumption of red meat from small cetaceans, therefore, could pose a health problem for not only pregnant women but also for the general population.

Administration, Oral↗
PubMed2004

Observation by an air-shower array in Tibet of the multi-TeV cosmic-ray anisotropy due to terrestrial orbital motion around the Sun.

We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g., the solar modulation effect. This is the highest-precision measurement of the Compton-Getting anisotropy ever made.

Journal Article↗
PubMed2004

Contamination by mercury and cadmium in the cetacean products from Japanese market.

Cetaceans hunted coastally in Japan include several species of odontocete (dolphins, porpoises and beaked whales), and fresh and frozen red meat and blubber, as well as boiled internal organs, such as liver, lung, kidney and small intestine, are still sold for human consumption. Furthermore, red meat and blubber products originating from mysticete minke whales caught in the Antarctic and Northern Pacific are also sold for human consumption. We surveyed mercury and cadmium contamination levels in boiled liver, lung, kidney and red meat products being marketed in Japanese retail outlets. We also analyzed the DNA of these products to obtain information concerning gender and species. Total mercury (T-Hg) and methyl mercury (M-Hg) contamination levels in all the cetacean products were markedly higher in odontocete species than in mysticete species, and slightly higher in females than in males. T-Hg contamination in the organs was seen in the following order: boiled liver>boiled kidney=boiled lung>red meat. In particular, T-Hg concentrations in the boiled liver were high enough to cause acute intoxication even from a single ingestion: the mean +/-SD (range) of T-Hg was 388+/-543 (0.12-1980) microg/wetg. In contrast, although M-Hg contamination in the liver was not markedly higher than that in other organs, M-Hg contamination was in the following order: boiled liver>odontocete red meat>boiled kidney>boiled lung. The contamination levels of T-Hg and M-Hg in odontocete red meat, the most popular whale product, were 8.94+/-13.3 and 5.44+/-5.72 microg/wetg, respectively. These averages exceeded the provisional permitted levels of T-Hg (0.4 microg/wetg) and M-Hg (0.3 microg/wetg) in marine foods set by the Japanese Ministry of Health, Labor and Welfare by 22 and 18 times, respectively, suggesting the possibility of chronic intoxication by T-Hg and M-Hg with frequent consumption of odontocete red meat. Cadmium contamination levels in boiled liver, kidney and lung were 8.59+/-12.0, 10.4+/-8.6 and 1.66+/-1.27 (microg/wetg), respectively.

Animals↗
PubMed2003

Direct observation of charge transfer in double-perovskite-like RbMn[Fe(CN)6].

The charge density distribution has been determined for a transition metal cyanide, RbMn[Fe(CN)(6)], by means of the maximum entropy-Rietveld method combined with the highly angularly resolved synchrotron radiation x-ray powder diffraction at SPring-8 BL02B2. We directly observed a charge transfer from the Mn site to the Fe site in the low-temperature phase. On the basis of a local density approximation calculation, we discuss the origin for the anisotropic bonding electron distribution around the Mn3+ ion in the low-temperature phase.

Journal Article↗
PubMed2003

Mercury contamination in the red meat of whales and dolphins marketed for human consumption in Japan.

Cetacean products sold for human consumption in Japan originate from a wide range of whale, dolphin, and porpoise species caught off several areas of the Japan coast, Antarctic and North Pacific Oceans. We surveyed the total mercury (T-Hg) levels in red meat, the most popular cetacean products in Japan. We also analyzed the DNA of these to obtain information regarding species. According to the genetic analysis, the red meats originating from nine species of odontocete and six species of mystecete were sold in Japanese markets. T-Hg concentrations in all odontocete red meats (0.52-81.0 microg/wet g, n = 137) exceeded the provisional permitted level of T-Hg in marine foods set by the Japanese government (0.4 microg/wet g). The highest and second highest levels of T-Hg in the red meats were found in the false killer whale (81.0 microg/wet g) and striped dolphin (63.4 microg/wet g), respectively. These concentrations of T-Hg exceeded the permitted level of T-Hg by about 200 and 160 times, respectively, suggesting the possibility of chronic intoxication by methyl mercury due to frequent consumption of odontocete red meats. The T-Hg concentration levels were higher in odontocete species such as Baird's beaked whales and pilot whales caught off southern areas than those caught off northern areas, probably reflecting a higher Hg concentration in the seawater and/or their diet (squid and fish) in the southern area. On the other hand, T-Hg concentrations in all mystecete red meat samples except for one (0.01-0.54 microg/ wet g, n = 62) were below the permitted level of T-Hg, probably reflecting their lower trophic levels.

Animals↗
PubMed2003

Charge ordering and spin frustration in AlV2-x CrxO4.

The relationship between charge and spin degrees of freedom in a geometrically frustrated system, AlV2-xCrxO4 spinel, is investigated. Upon Cr doping, the charge-ordered phase of AlV2O4 is rapidly suppressed and a charge-disordered phase grows up instead. It is found that the magnetic ground state is a spin-glass state dominated by geometrical frustration for both phases, but larger spin entropy remains down to low temperatures in the charge-ordered phase, possibly owing to its two-dimensional character.

Journal Article↗
PubMed2002

Orthodontic appliances made of organic polymer used in the metal allergic patient can withstand orthognathic surgery.

We developed an orthodontic appliance completely made of organic polymer. The appliance was used for many years and proved very effective. It was used for the treatment of patients with metal allergy, and as a result, it is believed to be the best choice for treating metal allergies. In this report, we are presenting a surgical case with Class III malocclusion for a patient with metal allergy, and the concept of the appliance is briefly discussed.

Adolescent↗
PubMed2001

Semi-quantitative RT-PCR analysis of environmental influence on P450scc and PNMT mRNA expression in rat adrenal glands.

Environmental influence on brain function, particularly spatial learning and memory, has been extensively investigated, but little is known about the influence of environmental conditions on the functions of peripheral organs. In the present study, the effects of different housing conditions on the steady-state levels of mRNAs encoding cholesterol side-chain cleavage enzyme (cytochrome P450scc) and phenylethanolamine N-methyltransferase (PNMT) in adrenal glands was examined to investigate the environmental influence on both adrenocortical and adrenomedullary functions. Behavioral changes of the animals housed in different conditions were first examined to assess the relevance of environmental manipulation used. In consistent with previous findings, housing of the animals in enriched conditions resulted in the significant reduction of spontaneous motor activity (locomotor activity and rearing) in comparison with housing in isolated conditions, thus indicating the relevance of housing conditions used in this work for investigating the environmental influence on adrenal function. Then, the effects of these housing conditions on P450scc and PNMT mRNA levels in adrenal glands were examined using semi-quantitative RT-PCR method. In comparison with the isolated group, the enriched group showed significantly higher levels of P450scc mRNA. In contrast, PNMT mRNA levels in the enriched group were significantly lower than those in the isolated group. These results propose the possibility that the environmental conditions may cause differential alterations in adrenocortical and adrenomedullary functions, although their possible association with behavioral changes still remains to be elucidated.

Adrenal Glands↗
PubMed2001

Involvement of nuclear transcription factor Sp1 in regulating glucose transporter-1 gene expression during rat trophoblast differentiation.

Glucose transporter-1 (GLUT1) is important in placental glucose transport. However, the mechanism of regulation of placental GLUT1 expression remains to be elucidated. We show here that the level of GLUT1 protein in rat choriocarcinoma cells (Rcho-1) decreased during differentiation. To analyze the regulatory mechanism of rat GLUT1 (rGLUT1) gene expression, we transfected rGLUT1 promoter-chloramphenicol acetyltransferase constructs into Rcho-1 cells. Deletion analysis of the rGLUT1 promoter suggested that the region -76/-53 bp was essential for basal transcriptional activity. Electrophoretic mobility shift assays showed that transcription factors Sp1 and Sp3 bound two GC boxes in the region -99/-33 bp of the rGLUT1 promoter. Mutation analysis of the Sp1 binding sites revealed that the promoter-proximal site located between -76 and -53 bp was essential for basal rGLUT1 promoter activity. Furthermore, the decreased level of GLUT1 may result from a decreased level of Sp1 during differentiation. These findings suggest that Sp1 is involved in the regulation of rGLUT1 gene expression during rat trophoblast differentiation.

Animals↗
PubMed2001

Evidence for Pb-O covalency in tetragonal PbTiO3.

Accurate charge-density distributions of cubic and tetragonal PbTiO3 and BaTiO3 have been obtained by the MEM(maximum entropy method)/Rietveld analysis using synchrotron-radiation powder data. The Pb-O bonds in tetragonal PbTiO3 show rather strong covalency, while those in cubic PbTiO3 are ionic. This is the clear evidence of the Pb-O hybridization in tetragonal PbTiO3, which has been theoretically predicted as a key factor of much larger ferroelectricity of this substance than that of BaTiO3. Tetragonal PbTiO3 forms a layered structure of a two-dimensional covalent-bonding network consisting of the Ti-O5 pyramid.

Journal Article↗
PubMed2001

Expression of IL-1 beta and IL-8 by human gingival epithelial cells in response to Actinobacillus actinomycetemcomitans.

The interaction between epithelial cells and microorganisms is the most important step in bacterial infections. Epithelial cells in response to exposure to pathogenic bacteria produce cytokines that initiate inflammation. However, little is known about the cytokine response of gingival epithelial cells to periodontopathogenic bacteria. Actinobacillus actinomycetemcomitans is thought to play a significant role in the initiation of periodontitis because of its bacteriological characteristics. In the present study, we investigated the cytokine induction by human gingival epithelial cells (HGEC) following exposure to A. actinomycetemcomitans in comparison with human gingival fibroblasts (HGF) in culture. Northern blot analysis showed that mRNAs of interleukin 1beta (IL-1beta) and IL-8, but not IL-6, in HGEC were induced in response to A. actinomycetemcomitans. Secretion of IL-8 by HGEC was also increased following A. actinomycetemcomitans challenge, whereas production of IL-1beta could not be detected. The levels of IL-8 and its mRNA were increased depending on the concentration of A. actinomycetemcomitans. The co-culture with HGF and A. actinomycetemcomitans resulted in an increase in the levels of IL-6 and IL-8 mRNA in HGF. However, HGF exposed to A. actinomycetemcomitans, showed no expression of IL-1beta mRNA. These findings demonstrated that HGEC and HGF stimulated with A. actinomycetemcomitans have different profiles in cytokine mRNA expression. Furthermore, A. actinomycetemcomitans may play an important role in amplifying the local immune response and in initiating inflammatory reaction through release of IL-8 from gingival epithelial cells.

Aggregatibacter actinomycetemcomitans↗
PubMed2001

Profenofos metabolites in human poisoning.

Profenofos and its metabolites were determined in a case of fatal poisoning. Little profenofos and large amounts of metabolites were detected by gas chromatography/flame photometric detection in the acid extracts of blood and urine after methylation with diazomethane. Four major metabolites containing phosphorus were identified with the synthesized metabolites, namely, despropylated profenofos, desethylated profenofos and des-S-propylated profenofos, respectively. 4-Bromo-2-chlorophenol (BCP), an aryl moiety of profenofos, was also determined in blood and urine with high performance liquid chromatograph (HPLC) as free or conjugated metabolites.

Aged↗