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I Yokota

Publications and source records attributed to I Yokota.

At least 19 recordsLinked to original sources
PubMed2003

Dissociation states of collagen functional groups and their effects on the priming efficacy of HEMA bonded to collagen.

Applying 2-hydroxyethylmethacrylate (HEMA) solution to etched dentin enhances the bonding of resin to dentin. However, the principal adhesion mechanisms have not yet been identified. In this study, we examined the dissociation states of the collagen functional groups of the side-chain amino acid residues and their effects on the bond strength of resin to etched dentin primed by the HEMA solution. The bond strength was strongly dependent upon the dissociation state of the collagen functional groups. Inhibiting the dissociation of the carboxylic acid or the amine of a collagen functional group resulted in increased bond strength of resin to collagen. By understanding the significance of inhibiting the dissociation state, we can better design and develop more effective and efficient primer and bonding agents.

Adhesiveness↗
PubMed2001

The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes (JSGIT): initial aims and impact of the family history of type 1 diabetes mellitus in Japanese children.

The Japanese Study Group of Insulin Therapy for Childhood and Adolescent Diabetes (JSGIT) was established in July 1994 with the chief aim to improve the quality of therapy for type 1 diabetes in children, an entity far less common in Japan than in Europe. We proposed four initial research topics: (i) to determine the current status of medical care and glycemic control in Japanese children with type 1 diabetes mellitus; (ii) to standardize the measurement of hemoglobin A1c; (iii) to establish a registry of a large cohort of patients in order to enable prospective studies to improve the quality of therapy for children with type 1 diabetes in Japan; and (iv) to enable participants of the JSGIT to hold a workshop twice annually. We registered a total of 736 patients from 45 hospitals throughout Japan. Intervention via insulin treatment was instituted after 2 yr for those patients whose hemoglobin A1c level was more than 8.1%. The proportion of patients receiving multiple insulin injections increased after intervention; however, average hemoglobin A1c in females remained significantly higher than in males. We identified two forms of diabetes in Japanese children: a rapidly progressive form and a more slowly progressive form. There was a significantly higher prevalence of a family history of diabetes in first-degree relatives in the slowly progressive form. These preliminary findings are the result of the first collaborative study of childhood diabetes in Japan.

Journal Article↗
PubMed2001

Paradoxical weight loss with extra energy expenditure at brown adipose tissue in adolescent patients with Duchenne muscular dystrophy.

We examined the energy expenditure in patients with Duchenne muscular dystrophy(DMD) to evaluate the cause of the paradoxical weight loss observed in large numbers of adolescent patients before any obvious impairment of their swallowing function. In the morning, resting energy expenditure (REE)/m(2) was almost the same as that in normal controls despite a reduction in fat-free mass (FFM); thus, REE/m(2)/FFM was significantly increased in patients (median, 21.2 kcal/m(2)/FFM kg; range, 17.7 to 44.2, P =.012). A thermographic examination in the morning showed an obvious elevation of the body surface temperature on the back. This phenomenon was consistent with a paradoxical fall in the low frequency (LF)/high frequency (HF) ratio at night analyzed using the inter-RR spectrum by 24-hour electrocardiogram, which indicated relative activation of the sympathetic nervous system. The urinary secretion of norepinephrine at night was also significantly greater in patients (median, 0.119 microg/kg/h; range, 0.061 to 0.219, P =.011). These results suggest that paradoxical activation of the sympathetic nervous system may accelerate the production of heat in brown adipose tissue (BAT) and increase the level of energy consumption in patients, and that adolescent DMD patients may require greater caloric intake than expected to maintain body weight, which is important to improve the prognosis of their respiratory function.

Adipose Tissue, Brown↗
PubMed2001

Gender-specific occurrence of West syndrome in patients with pyruvate dehydrogenase complex deficiency.

Pyruvate dehydrogenase complex (PDHC) deficiency, a major cause of congenital lactic acidemia in children, usually is complicated by seizures, and, in some patients, West syndrome has occurred. We diagnosed 60 patients with PDHC deficiency, including equal numbers of affected males and females. We studied the clinical features in 10 patients with West syndrome caused by PDHC deficiency, and examined the relation to the mutation of the E(1)alpha subunit, representing the great majority of PDHC deficiencies. Among 30 boys and 30 girls with PDHC deficiency,1 boy and 9 girls had West syndrome, even though overall West syndrome shows a slight male preponderance. Therefore, West syndrome associated with PDHC deficiency occurred in 9 of 30 female patients (33%), but in only 1 of 30 male patients (3%). The frequency of West syndrome in patients with PDHC deficiency was significantly higher in females than in males(p<0.05). Lactate concentrations in blood and CSF should be measured in female patients with West syndrome as a screening test for PDHC deficiency, because of gender-specific occurrence of West syndrome caused by PDHC deficiency.

Acidosis, Lactic↗
PubMed2001

Studies on the evaluation of municipal waste management systems.

The municipal waste disposal system is at a turning point now, because full-scale efforts are demanded to approach the goal of 'the construction of a waste-recycling society'. An attempt was made to evaluate municipal solid waste management systems with easier indexes in the model area. This study includes two evaluation systems. One evaluation system (case 1) is based on the analysis of waste management costs. Different waste disposal systems can be easily evaluated by comparing the waste disposal costs associated with them. However, it seems risky to rate cities only by the results of an analysis of the waste disposal cost data, since the municipalities build, acquire or expand facilities independently from one another. The associated costs are not summed in a uniform way by all municipalities and for other reasons. The other evaluation system (case 2) is based on the 'amenity and comfort ranking of cities' (Keizai 1998). Judgment by one evaluation index alone for a waste disposal system seems risky since the data in that case are insufficient for proper evaluation of a city. Hence, it is desirable to use two or more indices representative of a future ideal system. The results of the study demonstrated that Toyo Keizai's method of 'amenity and comfort ranking of cities' is better than the method of comparing solid waste management costs.

Cities↗
PubMed2000

Application of high resolution microfocus X-ray CT for the observation of human tooth.

The calcification degree of extracted human teeth was observed by using high resolution microfocus X-ray CT. As samples, upper and lower first premolars extracted from a 21-year-old female were used. The computed tomograms were produced by high resolution microfocus X-ray CT with a open vacuum X-ray source, rotating sample stage, and image sensor. The distinction between enamel and dentin was very clear, and the shape of the pulp cavity was also clearly identified. The secondary dentin was visible in the circumpulpal dentin. The color map displays showed the heterogeneity of the calcification degree not only in the dentin but also in the enamel. The enamel was divided into three layers according to the calcification degree. High resolution microfocus X-ray CT was very useful for the observation of the internal structure of human teeth without destroying the samples.

Adult↗
PubMed1999

Concomitant administration of sodium dichloroacetate and thiamine in west syndrome caused by thiamine-responsive pyruvate dehydrogenase complex deficiency.

We treated a female patient with West syndrome caused by thiamine-responsive pyruvate dehydrogenase complex (PDHC) deficiency. Infantile spasms occurred in association with elevated blood and CSF lactate concentrations; these symptoms disappeared when lactate concentrations had been lowered by treatment with concomitant sodium dichloroacetate (DCA) and high dose thiamine. Sequencing the patient's PDHC E(1)alpha subunit revealed a substitution of serine for glycine at position 89 in exon 3 (G89S). This mutation must be a de novo mutation because it was not found in either parents' genome DNA. To our knowledge, five previously described patients with PDHC deficiency have displayed the West syndrome. All six known patients, including our own, were female, even though an approximately equal number of males and females have been identified with PDHC deficiency and overall West syndrome occurs somewhat more frequently in males. These results indicated that West syndrome occurred more frequently in female patients with PDHC deficiency. It is suggested that lactate concentration should be measured in patients with West syndrome for potential PDHC deficiency, especially in females.

Amino Acid Substitution↗
PubMed1999

Dynamic changes in serum leptin concentrations during the fetal and neonatal periods.

We investigated the dynamics of the leptin concentration throughout the perinatal period. Serum leptin concentrations in venous cord blood at different gestational ages were measured in 20 preterm and 139 term newborns, as well as in 143 pregnant women and 24 term newborns at approximately 6 d of life. Leptin concentrations in preterm newborns (mean 4.6+/-6.9 ng/mL) were lower than those in term newborns (mean 19.6+/-14.3 ng/mL) and tended to increase according to gestational age and birth weight, especially from the late stage of gestation. Leptin concentrations in pregnant women increased from the first trimester and then remained higher than those in non-pregnant women throughout the remainder of pregnancy even after controlling for body mass index. The leptin concentrations of newborns declined rapidly and were extremely low by approximately 6 d of life (mean 1.9+/-1.1 ng/mL). These results suggest that fetuses might produce a part of circulating leptin in their own adipocytes and that the relatively high leptin concentrations at birth and their rapid decline in the early neonatal period might reflect the dramatic changes of the hormonal and nutritional state during the perinatal period.

Body Mass Index↗
PubMed1999

Development changes in long-form leptin receptor expression and localization in rat brain.

The expression and localization of long-form leptin receptor (OB-Rb) were studied immunocytochemically in the brain of fetal and adult rats using a polyclonal antibody that specifically recognized OB-Rb. At 14 days of gestation, immunoreactive cells were observed in the ventricular layer, which contains premature neuronal cells. At 18 days of gestation, they were weakly stained but obvious in the paraventricular nucleus (PVN), and ependymal cells also showed immunoreactivity. At birth, the immunoreactivity of OB-Rb in the PVN seemed to be much lower than that in adult rats and remained low during the suckling period. Considering the presence of neuroendocrine and structural neuronal abnormalities in Lepob/Lepob mice with genetic leptin deficiency, these results suggest that the expression of OB-Rb in premature neuronal cells may have some function, and that the regulation of energy balance by leptin through hypothalamic regions, such as PVN, may not yet be developed in the perinatal period.

Aging↗
PubMed1999

Analysis of polymerization behavior of dental dimethacrylate monomers by differential scanning calorimetry.

The polymerization and copolymerization activity of dental monomers was investigated using the dynamic differential scanning calorimetry (DSC) method. As aliphatic dimethacrylate monomers, ethyleneglycol dimethacrylates with different lengths of ethyleneglycol and urethane dimethacrylates were used. As aromatic dimethacrylates, Bis-GMA (2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane), BMPEPP (2,2-bis(4-methacryloxy poly-ethoxyphenyl)propane), and DMB (1,2-dimethacryloyloxy benzene) were used. Ethyleneglycol dimethacrylates showed sharp exothermic peaks, and the maximum temperatures (Tp) at the exothermic peaks of the DSC curves decreased according to the lengths of ethyleneglycols. Among urethane dimethacrylates, UDMA (dimethacryloxyethyl 2,2,4-trimethylhexamethylene diurethane) and DMPHU (di-(2-methacryloxypropyl) hexamethylene diurethane) showed sharp exothermic peaks, but DMEHU (di-(2-methacryloxyethyl) hexamethylene diurethane) showed an endothermic peak as well as exothermic peaks. This suggests that reactions other than polymerization occurred in the case of DMEHU. The polymerization activity of aromatic dimethacrylates was lower than that of ethyleneglycol dimethacrylates and urethane dimethacrylates. The copolymerization activity of TEGDMA (triethyleneglycol dimethacrylate) and DMB was also investigated using the dynamic DSC method. The DSC curves of the copolymerization between DMB and UDMA or BMPEPP showed broad peaks, but the DSC curves of the copolymerization between TEGDMA and UDMA or BMPEPP showed sharp peaks. The copolymerization activity of TEGDMA was better than that of DMB.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1998

Effect of growth hormone on the translocation of GLUT4 and its relation to insulin-like and anti-insulin action.

To elucidate the effect of growth hormone (GH) on the insulin signal transduction pathway leading to the translocation of glucose transporter-4 (GLUT4), we constructed Chinese hamster ovary cells that overexpressed GH receptor and GLUT4. Treatment with GH triggered GLUT4 translocation, and this translocation was completely inhibited by wortmannin. GH-induced GLUT4 translocation reached a maximum level after 30 min, and then gradually decreased and returned to the basal level after 2 h. Tyrosine phosphorylation of JAK2 also became maximal after 30 min and then gradually decreased. In contrast, GLUT4 translocation remained unchanged for 2 h after insulin treatment, and tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) also remained constant for up to 2 h. Chronic GH treatment had almost no effect on insulin-stimulated Akt kinase activation and GLUT4 translocation. These results suggest that GH and insulin translocate GLUT4 in a similar manner, at least in part, and the difference in translocation depends on the difference in the tyrosine phosphorylation of JAK2 and IRS-1. The anti-insulin action of GH after chronic GH treatment does not appear to be mainly due to the inhibition of GLUT4 translocation.

Androstadienes↗
PubMed1998

Thiamine-responsive lactic acidaemia: role of pyruvate dehydrogenase complex.

UNLABELLED: Lactic acidaemia is sometimes associated with a defect of the pyruvate dehydrogenase complex (PDHC), catalysing the thiamine-dependent decarboxylation of pyruvate. The activity of PDHC for different thiamine pyrophosphate (TPP) concentrations was determined in 13 patients with lactic acidaemia, clinically responsive to thiamine treatment in order to assess the role of PDHC in the aetiology of thiamine-responsive lactic acidaemia. Culture of lymphoblastoid cells and skin fibroblasts and muscle biopsies were performed in these 13 patients. The activity of PDHC to sodium dichloroacetate (DCA), known as the activator of PDHC, was also examined. Three groups were identified according to PDHC activity. Group 1 (two patients) displayed very low PDHC activity, which was not increased by DCA. This PDHC activity increased at high TPP concentrations. Group 2 (five patients) displayed below normal PDHC activity at low TPP concentrations, increased by DCA. This PDHC activity became normal at high TPP concentrations. PDHC deficiency in these patients of groups 1 and 2 was due to a decreased affinity of PDHC for TPP. Group 3 included six patients with normal PDHC activity at low as well as high TPP concentrations. This PDHC activity was increased by DCA. CONCLUSION: High concentrations of TPP may be required for maximal activity of PDHC in some patients with lactic acidaemia. The assay of PDHC activity, performed at a low concentration of TPP (1 x 10(-4)mM) allows selection of patients with thiamine-responsive lactic acidaemia.

Acidosis, Lactic↗
PubMed1998

Discrepant intracellular pH changes following intracellular Ca2+ increases induced by glutamate and Ca2+ ionophores in rat hippocampal neurons.

We investigated changes in intracellular pH (pHi) in relation to intracellular Ca2+ concentration ([Ca2+]i) in primary cultured hippocampal neurons treated with glutamate. [Ca2+]i and pHi were imaged with fluorescent dyes and confocal microscopy. Exposure to 1 mM glutamate for 10 min increased [Ca2+]i and evoked acidosis. These changes persisted for at least 60 min, even after removal of glutamate. The increase in [Ca2+]i and the acidosis were not observed in Ca2+-free solution and were attenuated in the presence of MK-801, an NMDA receptor antagonist. We also found that the increase in [Ca2+]i and acidosis could be induced by addition of Ca2+ to the extracellular solution in the cells pretreated with glutamate in Ca2+-free solution, even if glutamate did not exist in the extracellular solution. On the other hand, ionomycin and Br-A23187, calcium ionophores, increased [Ca2+]i to almost the same level as glutamate and increased pHi. Extracellular Ca2+ was also indispensable for the increase in [Ca2+]i and the alkalosis. These results suggest the followings: 1) intracellular acidosis by glutamate is dependent on the presence of extracellular Ca2+; 2) the acidosis does not result from only the increase in [Ca2+]i; and 3) glutamate induces the irreversible disorder of regulatory mechanisms of [Ca2+]i not only by Ca2+-dependent process, but also by Ca2+-independent process.

Animals↗
PubMed1998

Baumkuchen map analysis to detect postural cerebral hypoperfusion with upright 99Tcm-HMPAO brain SPET.

We have evaluated a polar cortical flow Baumkuchen map (BK map), constructed from projection data by inwardly layering cortical flow stripes from the base to the apex, to detect postural cerebral hypoperfusion using 99Tcm-HMPAO brain SPET. A circular cortical perfusion outline was constructed from sinogram data at a 20% threshold; a ring was then formed by constructing an inner line with a radius equal to half that of the outer line. This ring on the transaxial image was superimposed onto the cortical image, then divided into 60 portions at 6 degrees intervals from the centre. The maximal number of counts per pixel within each sector was determined, translated into polar coordinate profiles and displayed as a polar map. We studied 11 patients with unilateral stenosis of the internal carotid artery or middle cerebral artery (MCA) and 7 patients without stenosis, using upright and supine (rest) 99Tcm-HMPAO brain SPET Cerebral perfusion was visibly altered on the BK maps of all 11 patients with arterial stenosis and on the transaxial images of 8 of them. A semi-quantitative analysis of the BK maps using a ratio of the counts in the regions of interest over the right and left MCA areas, showed that the mean of the ratios was significantly lower in the upright images than in the upright + rest and rest images (P = 0.0044 and 0.0033, respectively). Although the difference in the means of the ratios between the upright and upright + rest images was significant for both the BK map and transaxial image data (P = 0.0044 and 0.0051, respectively), the BK map was accurate in detecting changes in perfusion in the upright position. We conclude that BK map analysis is useful for detecting changes in patients examined using upright brain SPET.

Adult↗
PubMed1998

Comparison of GAD and ICA512/IA-2 antibodies at and after the onset of IDDM.

OBJECTIVE: Longitudinal changes in GAD antibody (Ab) and ICA512/IA-2 (ICA512) Ab were examined in relation to age at the onset of diabetes and autoimmunity against the thyroid gland. RESEARCH DESIGN AND METHODS: GADAb, ICA512Ab, and antithyroid autoantibody were examined at onset in 40 juvenile-onset IDDM patients (17 males, 23 females, age at onset 9.4 +/- 4.1 years, range 1.7-20). To assess the changes in antibody levels, 29 patients were followed up with sequential serum samples for up to 5 years. RESULTS: At onset, GADAb, ICA512Ab, and antithyroid autoantibody (thyroglobulinAb or thyroid peroxidaseAb) were found in 70, 58, and 25% of the 40 patients, respectively. Prepubertal patients (n = 21) had a significantly higher prevalence and index of ICA512Ab compared with pubertal patients (n = 19) (76 vs. 37%, P = 0.012, and 2.43 +/- 2.36 vs. 0.66 +/- 1.23, P = 0.011), while GADAb was more prevalent in pubertal patients (57 vs. 84%, P = 0.09). A longitudinal analysis of GADAb and ICA512Ab showed that GADAb levels declined more slowly than those of ICA512Ab (P = 0.008). Patients with continuous extremely high levels of GADAb also had high levels of antithyroid autoantibody. CONCLUSIONS: The measurement of ICA512Ab is useful in prepubertal patients, who often show rapid progression of the disease. The presence of autoimmunity against thyroid gland seems to influence the GADAb level but not the ICA512Ab level.

Adolescent↗
PubMed1998

[GAD antibody in IDDM].

Glutamic acid decarboxylase (GAD) catalyzes the formation of gamma-aminobutyric acid (GABA), which is a major transmitter in the central nervous system. Two forms of GAD (GAD65 and GAD67) are known to be expressed in human tissues and GAD65 is predominantly expressed in pancreatic beta-cells. Recent findings revealed that GAD functions as an autoantigen in human autoimmunity, especially in insulin-dependent diabetes mellitus (IDDM). GAD is a key antigen for the development of autoimmunity against beta-cells and the production of GADAb precedes other autoantibodies such as IAA and ICA512/IA-2Ab prior to the clinical onset of IDDM. At onset, GADAb is detected in 50-80% of patients using RIA or RBA method. Factors that influence the positivities and titers of GADAb at onset, such as onset age, sex, presence of autoimmunity against thyroid, HLA type, have been reported. After onset, GADAb titer decreased more slowly than that of ICA512/IA-2Ab. These findings suggest that autoantibodies against beta-cells, such as GADAb, may develop independently. The presence of GADAb in relatives of IDDM patients and NIDDM patients predicts the development of beta-cell destruction in combination with other anti-islet autoantibodies.

Autoantibodies↗