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T Sakata

Publications and source records attributed to T Sakata.

At least 19 recordsLinked to original sources
PubMed2006

The PDZ domain protein PDZK1 interacts with human peptide transporter PEPT2 and enhances its transport activity.

The proton-coupled peptide transporter PEPT2 (SLC15A2) mediates the high-affinity low-capacity transport of small peptides as well as various oral peptide-like drugs in the kidney. In contrast to its well-characterized transport properties, there is less information available on its regulatory mechanism, although the interaction of PEPT2 to the PDZ (PSD-95, DglA, and ZO-1)-domain protein PDZK1 has been preliminarily reported. To examine whether PDZK1 is a physiological partner of PEPT2 in kidneys, we started from a yeast two-hybrid screen of a human kidney cDNA library with the C-terminus of PEPT2 (PEPT2 C-terminus (PEPT2-CT)) as bait. We could identify PDZK1 as one of the positive clones. This interaction requires the PDZ motif of PEPT2-CT detected by a yeast two-hybrid assay, in vitro binding assay and co-immunoprecipitation. The binding affinities of second and third PDZ domains of PDZK1 to PEPT2-CT were measured by surface plasmon resonance. Co-immunoprecipitation using human kidney membrane fraction and localization of PEPT2 in renal apical proximal tubules revealed the physiological meaning of this interaction in kidneys. Furthermore, we clarified the mechanism of enhanced glycylsarcosine (Gly-Sar) transport activity in PEPT2-expressing HEK293 cells after the PDZK1 coexpression. This augmentation was accompanied by a significant increase in the V(max) of Gly-Sar transport via PEPT2 and it was also associated with the increased surface expression level of PEPT2. These results indicate that the PEPT2-PDZK1 interaction thus plays a physiologically important role in both oligopeptide handling as well as peptide-like drug transport in the human kidney.

Biological Transport↗
PubMed2006

Plasma protein S activity correlates with protein S genotype but is not sensitive to identify K196E mutant carriers.

BACKGROUND: Protein S (PS) is an anticoagulant protein that functions as a cofactor for activated protein C (APC), and congenital PS deficiency is a well-known risk factor for the development of deep vein thrombosis (DVT). Recently, we and others identified the K196E missense mutation in the second epidermal growth factor-like domain of PS as a genetic risk factor for DVT in the Japanese population. The incidence of this mutation is high in the Japanese population. OBJECTIVES: In the present study, we investigated the relationship between plasma PS activity and the presence of the K196E mutation. PATIENTS AND METHODS: We measured PS activity as a cofactor activity for APC in 1,862 Japanese individuals and determined the PS K196E genotype in this population. RESULTS: Individuals heterozygous for the mutant E-allele had lower plasma PS activity than wildtype subjects (mean +/- SD, 71.9 +/- 17.6%, n = 34 vs. 87.9 +/- 19.8%, n = 1,828, P < 0.0001). However, the PS activity of several heterozygous individuals (n = 8) was greater than the population average. In contrast, multiple wildtype subjects (n = 26) had PS activity less than 2 SD below the population mean, indicating that other genetic or environmental factors affect PS activity. CONCLUSIONS: Plasma PS activity itself is not suitable for identifying PS 196E carriers and other methods are required for carrier detection.

Adult↗
PubMed2004

Hypothalamic neuronal histamine regulates sympathetic nerve activity and expression of uncoupling protein 1 mRNA in brown adipose tissue in rats.

To clarify how hypothalamic neuronal histamine regulates peripheral energy expenditure, we investigated the effect of infusion of histamine into the third cerebral ventricle or discrete hypothalamic regions on sympathetic nerve activity and expression of uncoupling protein 1 (UCP1) mRNA in brown adipose tissue (BAT). Infusion of histamine (200 nmol) into the third cerebral ventricle of anesthetized rats significantly increased the electrophysiological activity of sympathetic nerves (P<0.01) and UCP1 mRNA expression in the BAT (P<0.05). Microinjection of histamine (10 nmol) into the paraventricular nucleus (PVN) and preoptic area (POA) produced similar significant increases in BAT sympathetic nerve activity (P<0.01 for each). By contrast, injection of histamine into the ventromedial hypothalamic nucleus or lateral hypothalamic area had no effect. We conclude that hypothalamic neuronal histamine may regulate energy expenditure in BAT through the activation of sympathetic nerves. The PVN and/or POA appear to be the principal hypothalamic sites that mediate the stimulatory effect of histamine on this efferent pathway.

Action Potentials↗
PubMed2004

Viscoelastic properties of the small intestinal and caecal contents of the chicken.

We measured the coefficients of viscosity, shear rates and shear stresses of chicken small intestinal and caecal contents, including solid particles, using a tube-flow viscometer. The coefficients of viscosity of chicken small intestinal and caecal contents were correlated negatively with their shear rates, a characteristic typical of non-Newtonian fluids. The coefficient of viscosity of the small intestinal contents was lower than that of the caecal contents at a shear rate of 1 s(-1). Chicken caecal contents were more viscous than pig caecal contents. The exponential relationship between shear stress and shear rate showed that chicken small intestinal and caecal contents had an apparent Herschel-Bulkley fluid nature. These results indicate that solid particles, including uric acid crystals, are mainly responsible for the viscosity of the digesta in the chicken.

Animal Feed↗
PubMed2004

IKBL promoter polymorphism is strongly associated with resistance to type 1 diabetes in Japanese.

Type 1 diabetes is a multifactorial disease in which the genes of the major histocompatibility complex (MHC) play a key role. Recently, non-human leukocyte antigen (non-HLA) genes in the class III region of this complex have been presumed to be associated with type 1 diabetes by linkage analyses. We investigated the possibility of the inhibitor of kappaB-like (IKBL, also known as 'NFKBIL1') gene as one of these candidates. We carried out a case-control study of 124 patients with type 1 diabetes and 330 healthy control subjects. The haplotypes of the IKBL promoter, i.e., PA (-263A, -63T), PB (-263A, -63A), PC (-263G, -63T), were assigned by the single-nucleotide polymorphisms at positions -263 and -63 from the transcription start site. The frequency of the wild-type haplotype, PA, was elevated, while that of the variant-type haplotype, PC, was lower in patients than controls. In two-locus analyses with HLA-DRB1 alleles, the PA haplotype showed linkage disequilibrium with the DRB1*0405 allele and the PC haplotype with the DRB1*1502 allele. A notable observation was that the PC haplotype was significantly associated with protection in the DRB1*1502-negative population. Our study indicates the first evidence of a possible independent association between type 1 diabetes and polymorphisms in the promoter of the IKBL gene.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Trabecular bone mass and bone formation are preserved after limb immobilisation in p53 null mice.

OBJECTIVES: To determine whether disruption of the p53 gene leads to preservation of trabecular bone volume (BV) after limb immobilisation. MATERIALS AND METHODS: Tibias of immobilised hind limbs of p53 gene knockout (p53(-/-)) and wild-type (p53(+/+)) mice were compared. Right knee joints of 8 week old mice were immobilised in full extension for 7 days. Trabecular structure and bone formation were similar in the p53(-/-) and p53(+/+) control groups. RESULTS: Immobilisation significantly reduced BV to 77% of the control in p53(+/+) mice, but no change was noted in p53(-/-) mice. After immobilisation, bone formation rate was significantly reduced in p53(+/+) but not in p53(-/-) mice. In bone marrow cell cultures the numbers of alkaline phosphatase positive colony forming units-fibroblastic and mineralised nodules were significantly reduced by immobilisation in p53(+/+) but not in p53(-/-) mice. Immobilisation enhanced p53 mRNA expression in marrow cells of p53(+/+) mice and increased terminal dUTP nick end labelling positive osteocytes and marrow cells in p53(+/+) but not in p53(-/-) mice. Lack of p53 in immobilised mice was associated with preservation of trabecular bone mass and bone formation and suppression of significant apoptosis of marrow cells. CONCLUSION: Disruption of the p53 gene preserves trabecular bone mass and leads to bone formation after limb immobilisation.

Animals↗
PubMed2003

bFGF administration lowers the phosphate threshold for mineralization in bone marrow stromal cells.

Basic fibroblast growth factor (bFGF) is a potent mitogen and acts as an autocrine/paracrine factor for osteoblasts. Long-term administration of bFGF in vivo increases osteoblast number and stimulates matrix formation, but induces hypophosphatemia and impairs matrix mineralization. The goal of this study was to examine the interaction between bFGF and low levels of organic phosphate in an effort to better understand the possible long-term therapeutic effects of bFGF. These data show that in vitro administration of bFGF accelerates the calcification process and lowers the phosphate threshold needed for successful bone nodule formation. This correlates well with the observed upregulation of mRNA production for alkaline phosphatase and osteocalcin at day 7. These findings help elucidate the mechanisms of bFGF action on bone marrow stromal cell differentiation and mineralization and indicate that the delay in mineralization observed in vivo may not be caused by decreased phosphate availability alone.

Alkaline Phosphatase↗
PubMed2003

Skeletal unloading induces resistance to insulin-like growth factor I on bone formation.

Skeletal unloading results in an inhibition of bone formation associated with a decrease in osteoblast number, impaired mineralization of bone, and altered proliferation and differentiation of osteoprogenitor cells. Although such changes are likely to be mediated by multiple factors, resistance to the growth-promoting action of insulin-like growth factor I (IGF-I) has been hypothesized to play an important role. To determine whether skeletal unloading induces resistance to IGF-I on bone formation, we examined the response of unloaded (hindlimb elevation) and normally loaded tibia and femur to IGF-I administration. To eliminate the variable of endogenous growth hormone production and secretion during exogenous IGF-I administration, we used growth hormone-deficient dwarf rats (dw-4). The rats were given IGF-I (2.5 mg/kg/day) or vehicle during 7 and 14 days of unloading or normal loading. This significantly increased the serum level of IGF-I in both the normally loaded and unloaded rats. Unloading did not affect the serum level of IGF-I in the vehicle-treated rats. IGF-I markedly increased periosteal bone formation at the tibiofibular junction of normally loaded rats. Unloading decreased bone formation in the vehicle-treated rats, and blocked the ability of IGF-I to increase bone formation. On the other hand, IGF-I increased periosteal bone formation at the midpoint of the humerus (normally loaded in this model) in both hindlimb-elevated and normally loaded rats. IGF-I significantly increased osteogenic colony number, total ALP activity, and total mineralization in bone marrow osteoprogenitor (BMOp) cells of normally loaded rats. Unloading reduced these parameters in the vehicle-treated rats, and blocked the stimulation by IGF-I. Furthermore, IGF-I administration (10 ng/ml) in vitro significantly increased cell proliferation of the BMOp cells isolated from normally loaded bone, but not that of cells from unloaded bone. These results indicate that skeletal unloading induces resistance to IGF-I on bone formation.

Animals↗
PubMed2003

Development and clinical application of nucleated red blood cell counting and staging on the automated haematology analyser XE-2100.

We initially developed a new flow cytometric (FCM) reference method for the enumeration and staging of nucleated red blood cells (NRBC) in 1997 [Wang et al., 1998 (XIth International Symposium on Technological Innovations in Laboratory Haematology, Banff, Canada, 1998); Tsuji et al., 1999 (Cytometry, 1999)]. The method used CD45 antibody and propidium iodide staining to separate NRBCs from other cells. Accuracy and precision were enhanced because larger numbers of cells were counted than was possible with the manual method. We also developed a method for automated NRBC counting on a haematology analyser, the XE-2100 (Wang, 1988). NRBC were separated from other cells using a special lysing buffer and a fluorescent dye. The XE-2100 was found to detect peripheral and cord blood NRBC accurately and precisely when compared with cell morphology or FCM control methods. The FCM NRBC staging method was established through the identification of different NRBC populations following the novel staining and lysing method. To evaluate the method further, we sorted samples containing NRBCs using a FACSort and investigated NRBC staging on the Sysmex XE-2100 based on the cell sorting results. Data were analysed using special software (ida). First, we used the data in various parameter combinations. We then established gates to classify the NRBC populations. Finally, we analysed blood specimens from patients with different types of diseases to explore possible clinical applications.

Blood Cells↗
PubMed2003

Population-based distribution of plasminogen activity and estimated prevalence and relevance to thrombotic diseases of plasminogen deficiency in the Japanese: the Suita Study.

Reduced plasminogen activity with a normal level of antigen is commonly observed in Japanese individuals. The first reported patient with plasminogen deficiency was accompanied with deep vein thrombosis. The present study examines whether heterozygous or homozygous deficiency of plasminogen is a risk factor for thrombotic disease. This study measures the plasminogen activity of 4517 individuals in the general population, determines the cut-off to define plasminogen deficiency, and identifies plasminogen deficiencies in the control groups and thrombotic disease groups. In another study, we examined the phenotypes of consecutive patients with homozygous plasminogen deficiency detected in our hospital. We found 173 and two of 4517 individuals to have heterozygous and homozygous deficiency with normal plasminogen antigen level, respectively, and 19 to have heterozygous deficiency with reduced antigen levels. The incidence of plasminogen deficiency in an age- and sex-matched control group (13/324, 4.01% for deep vein thrombosis or 13/330, 3.94% for stroke) selected from the 4517 individuals was not significantly different from those in patients with deep vein thrombosis (3/108, 2.78%) or cardioembolic stroke (6/110, 5.55%). Among 19 patients with homozygous plasminogen deficiency showing about 10% plasminogen activity, none had deep vein thrombosis. These findings indicate that neither heterozygous nor homozygous plasminogen deficiency constitutes a significant risk factor for thrombotic disease.

Aged↗
PubMed2003

Food texture differences affect energy metabolism in rats.

Dietary factors such as taste and nutrients are known to affect satiety and energy balance. We hypothesized that food texture might contribute to the regulation of energy metabolism through the process of mastication in the oral cavity as well. The effects of long-term feeding of different-textured pellets on body weight gain, adiposity, and thermogenesis were assessed. From weaning at 4 wks, rats were divided into 2 groups fed on either standard (controls) or soft pellets (soft-fed) that required less chewing with the same nutritional composition. At 26 wks, the soft-fed rats showed greater adiposity than did the controls. Daily food intake did not differ between the 2 groups. The increase in body temperature following feeding was significantly lower in the soft-fed rats. These results suggested that food texture affected energy metabolism by changing post-prandial thermogenesis. The long-term deficiency of thermogenesis associated with soft foods resulted in a greater tendency toward obesity.

Adipose Tissue↗
PubMed2002

Serum thymidine kinase and soluble interleukin-2 receptor predict recurrence of malignant lymphoma.

Before and after therapy, serum thymidine kinase (TK) and soluble interleukin-2 receptor (sIL-2R) were serially determined in 28 patients with malignant lymphoma (ML). In 15 patients achieving and maintaining complete remission (CR) for more than 2 years, serum TK and sIL-2R were unchanged or decreased gradually. In contrast, logarithmic linear increases of TK and sIL-2R were observed in 13 relapsed patients. The increments of the serum markers occurred more than 10 months before the relapse. A significant positive correlation between the slope of the line for TK and that for sIL-2R was noted. The doubling time for TK estimated from the slope also showed a positive correlation with that for sIL-2R. Taken together, serum TK and sIL-2R were shown to be quite sensitive and interrelated serum markers for the recurrence of ML. Slopes of logarithmic linear increase, which are proper and specific for the individual patients, are inversely correlated with the doubling time and reflect proliferation of ML. We conclude that serum TK and sIL-2R are better predictors of relapse than LDH and the international prognostic index (IPI).

Adult↗
PubMed2002

Stage-dependent changes in trabecular bone turnover and osteogenic capacity of marrow cells during development of type II collagen-induced arthritis in mice.

Rheumatoid arthritis (RA) is a disease characterized by inflammatory polyarthritis leading to destruction of the joints and reduction in bone mass. However, the relationship between bone mass and turnover is not yet clear in RA patients. To clarify the effect of bone turnover and marrow osteogenic capacity on mass and structure during the development of arthritis, we examined DBA1/J mice for 8 weeks after the first immunization with bovine type II collagen at the age of 9 weeks. Localized arthritis developed at 4 weeks and advanced arthritis at 6 weeks postimmunization. Urinary deoxypyridinoline levels in arthritic mice were significantly higher at 4 weeks, and levels were maintained thereafter. Their serum osteocalcin levels were significantly reduced compared with controls at 2 and 6 weeks, but did not differ significantly from those in the control group at 4 and 8 weeks. Three-dimensional (3D) trabecular bone volume of the proximal tibia measured by 3D microcomputed tomography (micro-CT) in the arthritic mice became significantly lower at 4 weeks and decreased further at 6 weeks compared with controls. Parameters of 3D trabecular bone structure, such as structure model index and trabecular bone pattern factor, were increased at 4 and 6 weeks, respectively. Trabecular osteoclast number increased and bone formation rates decreased at 8 weeks. The number of total bone marrow cells (BMCs), adherent stromal cells, and area of mineralized nodule formation in the tibia of arthritic mice were significantly reduced compared with controls at 6 weeks. Numbers of total fibroblastic colony-forming units (CFU-f) and alkaline phosphatase (ALP)-positive CFU-f colonies also decreased. However, the values of these osteogenic parameters corrected for the total BMCs and/or adherent stromal cells did not differ significantly between the arthritic and control groups. These data indicate that an increase in bone resorption led to the reduction in trabecular bone mass and deterioration of 3D structure during the localized arthritic stage. The reduction in bone marrow osteogenic potential in the advanced arthritic stage was due to the reduction in the number of total bone marrow cells, and differentiation of osteogenic cells was apparently unaffected. The reduction in bone formation may not be substantial in this arthritic model.

Animals↗
PubMed2002

Histidine induces lipolysis through sympathetic nerve in white adipose tissue.

BACKGROUND: Hypothalamic neuronal histamine has been shown to increase lipolysis in white adipose tissue. The present study aimed to clarify whether peripheral loading with L-histidine, a precursor of neuronal histamine, may affect lipid metabolism in adipose tissue. MATERIALS AND METHODS: The in vivo microdialysis study was used to assess lipolysis in rat epididymal adipose tissue by measuring the release of glycerol in response to administration of L-histidine. In addition, electrophysiological measurements were performed to record changes in activity of sympathetic nerve innervating adipose tissue following histidine treatment. RESULTS: Sequential administration of isoproterenol, a beta-adrenoceptor agonist, through the microdialysis cannula at concentrations of 10(-)8 to 10(-6) M increased the glycerol concentration in the dialysate dose-dependently (P < 0.05). Intraperitoneal administration of L-histidine at a dosage of 0.35 mmol kg(-1) also increased the glycerol concentration compared to that of phosphate buffered saline (P < 0.05). Concomitantly, the administration of histidine increased the serum concentration of free fatty acid compared to control treatment (P < 0.05). The accelerating effects of histidine on lipolysis were mimicked by the infusion of 10(2) nmol rat(-1) L-histamine into the third cerebroventricle (P < 0.05). Electrophysiological measurement demonstrated that administration of histidine at a dosage of 0.35 mmol kg(-1) increased the activity of efferent sympathetic nerve, innervating adipose tissue more than the infusion of phosphate buffered saline (P < 0.05). CONCLUSION: The present results indicate that histidine accelerates lipolysis in white adipose tissue through activation of the sympathetic nerve. The regulation of lipolysis may therefore involve histamine neurons in the brain, probably through the conversion of L-histidine to histamine in the hypothalamus.

Adipose Tissue↗
PubMed2001

A role for neuromedin U in stress response.

Neuromedin U (NMU) is a hypothalamic peptide that has been recently found to reduce food intake, but few is known about its other functions in the central nervous system. We here studied behavioral activities induced by an intracerebroventricular (ICV) administration of NMU in rats and mice. NMU increased gross locomotor activity, face washing behavior, and grooming. NMU-induced stress response was significantly abolished by pretreatment with an antagonist of corticotropin-releasing hormone (CRH), alpha-helical CRH (9-41) (alpha-hCRH), or anti-CRH IgG. NMU did not induce locomotor activity in CRH knockout mice. NMU that interacts anatomically and/or functionally with the CRH system is a novel physiological regulator of stress response.

Animals↗