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Biomedical subjects

Y Oshida

Publications and source records attributed to Y Oshida.

At least 37 records · Page 2Linked to original sources
PubMed2001

Porcelain-metal bonding: part I. Effects of repeated baking process.

A plurality of repeated porcelain-baking procedures are normally practiced in order to achieve the final adjustment metal-porcelain restorations. By increasing the number of baking cycles, the undesired internal strain would be built-up, causing the reduction of mechanical properties and deterioration of color characteristics. However the extensive studies on such deterioration have not been done. In this study, effects of numbers (up to 10 times) of repeated baking cycles on baking shrinkage, surface roughness, bend strength, color changes and internal microstructure were investigated when opaque, body and enamel was individually applied or when a triple-player comprising of these three porcelains was repeatedly applied. It was concluded that (1) the bend strengths increased by increasing baking cycles, (2) the average surface roughness decreased by increasing number of baking procedures, (3) changes in color characteristics was very small in the Vintage halo porcelain system, and (4) since the pores entrapped in the porcelain remained even by increasing baking cycles, it is recommended to remove the surface pores before forming the next layer when handling the high viscous opaque porcelain.

Biomechanical Phenomena↗
PubMed2001

Initial contact angle measurements on variously treated dental/medical titanium materials.

The cell attachment to bioapplicable titanium surfaces is an important parameter in the area of clinical implant dentistry and medicine. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues contacting the implants. In this study, three titanium materials (commercially pure titanium - CPT -, Ti-6Al-4V, and TiNi) were treated mechanically, chemically, mechano-chemically, and thermally to produce concave surfaces with varying roughness. Using four media (distilled water, 1% NaCl aqueous solution, a suspension of human neutrophils, and a suspension of the MG-63 osteoblast-like cells), the initial contact angles were measured. Six readings (three drops each measured by two observers) were collected for each material and for each medium. The interclass correlation coefficients were used for the group comparisons. A one-way analysis of variance (ANOVA) and Tukey's HSD (honestly significant difference) statistical analyses were employed. It was found, for CPT, that (1) statistically, there were no significant differences among four media in contact angles, (2) the contact angle increased linearly with average roughness when the angles were higher than 45 degrees, and (3) the contact angle decreased linearly with roughness when the angle was less than 45 degrees.

Alloys↗
PubMed2000

Additive effects of estrogen deficiency and diabetes on bone mineral density in rats.

We investigated the combined effects of estrogen deficiency and diabetes on bone mineral density (BMD) and bone metabolism in rats. Ten-week-old, female rats were randomly divided into four groups: controls (C), an ovariectomized group (O), a streptozotocin-induced diabetic group (S), and a combined ovariectomy and streptozotocin-induced diabetic group (OS). The BMD of the lumbar spine and the femur were measured before grouping and at 23 weeks old. At the end of the experiment, blood samples were obtained via cardiac puncture, and bone gla protein (BGP), tartrate-resistant acid phosphatase (TRAP) and 1,25-dihydroxyvitamin D levels were measured. The rats in the C, O, S, and OS groups, in that order, had higher levels of BMD of the lumbar spine and femur at 23 weeks of age. The BGP levels in the S and OS groups were significantly lower than in C and O groups. Significantly higher 1,25-dihydroxyvitamin D was observed in the O group compared with the C, S and OS groups. No differences were obtained in TRAP among four groups. Our data suggest that the combined effects of estrogen deficiency and diabetes on BMD are not synergistic or counteractive but additive.

Alkaline Phosphatase↗
PubMed2000

Effects of walking on bone quality as determined by ultrasound in the elderly.

In the present study, measurements of broadband ultrasound attenuation (BUA) were used as indications of bone quality in elderly residents of an old people's home. To investigate the possibility of using number of steps walked as an indicator of the role played by exercise on bone quality, we studied the relationship between BUA and the number of steps, taken as a measure of the number of impacts against the ground placing a direct mechanical stress on the bones. The subjects were 59 healthy elderly women with a mean age of 78+/-8 years who had no impairments in walking or daily life. A statistical analysis of the relationship between age, number of steps, BUA, stride length, and walking speed revealed that number of steps and BUA declined with age, and that BUA increased with a greater number of steps. Among other factors, age was found to be negatively correlated with weight (r= -0.343, P<0.01), BUA (r=-0.542, P<0.001), total number of steps (r= -0.524, P<0.001) and past exercise habits (r=-0.425, P<0.001). There were positive correlations between BUA and total number of steps (r=0.606, P<0.001), walking speed (r=0.460, P<0.001), stride length (r=0.373, P<0.01) and past exercise habits (r=0.429, P<0.001). These results show that the benefit to bone quality increases the more a person walks in daily life. The above demonstrates that degree of walking activity is positively correlated to bone quality among the elderly. These results also suggest that, when investigating the relationship between exercise and bone quality, one should look not only at distance and walking speed, but also number of steps as the number of impacts against the ground that place a direct mechanical stress on the bones. This may prove to be a useful indicator of bone quality in future use.

Activities of Daily Living↗
PubMed2000

Exercise training prevents maturation-induced decreases in insulin receptor substrate-1 and phosphatidylinositol 3-kinase in rat skeletal muscle.

We have previously reported that exercise training prevents a maturation-induced decrease in insulin sensitivity and suggested that an improvement of insulin sensitivity by exercise training was attributable, in part, to an increase in insulin-sensitive GLUT-4 on the skeletal muscle plasma membrane. In this study, we examined the effects of maturation and exercise training on the gene expression and protein content of the components of post-insulin receptor signal transduction in rat skeletal muscle. Rats aged 3 weeks were sedentary or trained by voluntary running through 4 or 27 weeks of age, and then the rats in both the sedentary and trained groups were killed and the gastrocnemius muscle was immediately removed for analysis of mRNA and protein content. The concentration of mRNA and protein for insulin receptor substrate-1 (IRS-1) in sedentary rats significantly decreased with maturation (49% and 63%, respectively, at age 27 weeks v age 4 weeks), but in trained rats they did not decrease with maturation. Although the level of phosphatidylinositol 3-kinase (PI 3-kinase) mRNA in sedentary rats was not altered with maturation, PI 3-kinase protein in sedentary rats significantly decreased with maturation (73% at 27 weeks v 4 weeks). However, PI 3-kinase protein in trained rats did not decrease with maturation. These results suggest that the prevention of maturation-induced decreases in the protein content of IRS-1 and PI 3-kinase is involved in the mechanisms responsible for the improvement of insulin sensitivity by exercise training, and exercise training may affect transcriptional regulation of the IRS-1 gene and posttranscriptional regulation of PI 3-kinase expression.

Animals↗
PubMed2000

Nitric oxide decreases insulin resistance induced by high-fructose feeding.

The effect of nitric oxide (NO) on insulin resistance was studied in high-fructose-fed rats. A sequential hyperinsulinemic euglycemic clamp procedure was employed (insulin infusion rates: 3 and 30 mU/kg BW/min) in 12 high-fructose-fed rats and 12 chow-fed rats while awake. Half of the high-fructose-fed and the chow-fed rats, respectively, were continuously given sodium nitroprusside (SNP, 3 ng/kg BW/min) during the clamp study. Blood glucose was clamped at the fasting level in each rat. Plasma insulin levels during the 3 and 30 mU/kg BW/min insulin infusions were 30 and 400 microU/ml, respectively. Metabolic clearance rate of glucose (MCR) was regarded as an index of whole body insulin action. At both 3 and 30 mU/kg BW/min insulin infusions, high-fructose feeding showed a significant decrease in MCR compared with the chow-fed rats. However, decreased MCRs were stimulated by SNP administration and reached similar levels as the chow-fed rats. SNP infusion did not influence MCRs in the chow-fed rats. Therefore it could be concluded that NO can improve insulin resistance induced by high-fructose feeding.

Animals↗
PubMed1999

In vitro pharmacological profile of nonpeptide CRF1 receptor antagonists, CRA1000 and CRA1001.

We investigated pharmacological properties of CRA1000 (2-(N-(2-methylthio-4-isopropylphenyl)-N-ethylamino-4-(4-(3-fluoro phenyl)-1,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine) and CRA1001 (2-( N-(2-bromo-4-isopropylphenyl)-N-ethylamino-4-(4-(3-fluorophenyl)-1 ,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine), novel and selective antagonists for the corticotropin-releasing factor1 (CRF1) receptor. Both CRA1000 and CRA1001 inhibited [125I]ovine CRF binding to membranes of COS-7 cells expressing the rat CRF1 receptor with IC50 values of 30 and 38 nM, respectively, without affecting [125I]sauvagine binding to membranes of COS-7 cells expressing the rat CRF2alpha receptor. CRF elicited intracellular cyclic AMP (cAMP) accumulation in AtT-20 cells which express the CRF1 receptor but not the CRF2 receptor, and COS-7 cells expressing CRF1 or CRF2alpha receptors. The CRF-induced cAMP accumulation was inhibited by both CRA1000 and CRA1001, concentration-dependently, in AtT-20 cells and COS-7 cells expressing the CRF1 receptor, while these compounds did not attenuate the CRF response in COS-7 cells expressing the CRF2alpha receptor. CRF increased adrenocorticotropin (ACTH) secretion from AtT-20 cells, and CRA1000 and CRA1001 inhibited CRF-induced ACTH secretion, concentration-dependently, as did other CRF1 receptor antagonists. These results show that both CRA1000 and CRA1001 are potent and selective CRF1 receptor antagonists.

Adrenocorticotropic Hormone↗
PubMed1999

Cloning and characterization of a short variant of the corticotropin-releasing factor receptor subtype from rat amygdala.

We have identified and characterized a cDNA encoding a novel isoform of the corticotropin-releasing factor (CRF) receptor, referred to as CRF2alpha-tr, from the rat amygdala cDNA library. The nucleotide sequence of the cloned cDNA has a structure of an alternatively spliced form of the CRF2alpha receptor, which contains unspliced introns 6 and 7 in the message, and encodes a 236-amino-acid truncated protein that comprises three unique transmembrane domains. Northern blot analysis shows that the CRF2alpha-tr receptor is more strongly expressed in the rat amygdala, thalamus, and hypothalamus than the intact CRF2alpha receptor. Western blot analysis also reveals that the CRF2alpha-tr protein can be expressed in transfected COS-7 cells as well as CRF2alpha. Furthermore, this receptor binds rat/human CRF with almost the same low affinity (Kd = 12.7 nM) as the CRF2alpha and without accumulation of intracellular cAMP. Interestingly, it does not bind sauvagine or rat urocortin. These findings suggest that this truncated CRF receptor is the major isoform of CRF2alpha receptor mRNA transcripts in the amygdala and would mediate some functions of CRF pathways in the central nervous system.

Alternative Splicing↗
PubMed1999

Rat C peptide I and II stimulate glucose utilization in STZ-induced diabetic rats.

AIMS: To study the effects of physiological concentrations of rat proinsulin C peptide I and II, respectively, on whole body glucose utilization in streptozotocin diabetic and healthy rats. METHODS: A sequential insulin clamp procedure was used (insulin infusion rates 3.0 and 30.0 mU.kg-1.min-1) in awake animals. C-peptide infusion rates were 0.05 and 0.5 nmol.kg-1.min-1. Blood glucose was clamped at 7.7 +/- 0.3 mmol/l in the diabetic rats and at 3.9 +/- 0.1 mmol/l in the healthy rats. RESULTS: In diabetic rats infused at lower rates of C peptide and insulin, glucose utilization increased by 79-90% (p < 0.001) compared with diabetic animals infused with saline and insulin. Increasing the rate of C-peptide infusion tenfold did not elicit a statistically significant further increase in glucose utilization. C peptide I and II exerted similar effects. The metabolic clearance rate for glucose in the diabetic animals infused with C peptide was not different from that of the healthy rats. During high-dose insulin infusion (30.0 mU.kg-1.min-1) glucose utilization increased considerably and no statistically significant C-peptide effects were observed. About 85% of the increase in glucose utilization induced by C peptide could be blocked by treatment with N-monomethyl-L-arginine. CONCLUSIONS/INTERPRETATION: Physiological concentrations of homologous C peptide stimulate whole body glucose utilization in diabetic but not in healthy rats. C peptide I and II elicit similar effects. The influence of C peptide on glucose utilization may be mediated by nitric oxide.

Animals↗
PubMed1999

Insulin activation of pyruvate dehydrogenase complex is enhanced by exercise training.

We studied the effects of exercise training on the activity of the pyruvate dehydrogenase (PDH) complex in rat gastrocnemius muscle (experiment 1) and the response of the complex to glucose and insulin infusion (euglycemic clamp) in trained and sedentary rats (experiment 2). In experiment 1, half of the rats were randomly allocated as sedentary animals and the other half were trained by voluntary running exercise for 8 weeks. The total activity of the PDH complex was not affected by exercise training, and the activity state (proportion of the active form) of the PDH complex was decreased from 15.0%+/-2.4% to 7.5%+/-1.1% by exercise training. The activity of 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase ([3-HADH] an enzyme in beta-oxidation) was significantly higher in trained versus sedentary rats. In experiment 2, sedentary and trained rats were starved for 24 hours before performing the euglycemic clamp. Glucose and insulin infusion was performed by a euglycemic clamp (insulin infusion rate, 6 mU/kg/min) for 90 minutes. The PDH complex was inactivated to less than 1% in both sedentary and trained rats after 24 hours of starvation. The glucose infusion rate (GIR) during the euglycemic clamp was higher in trained versus sedentary rats. The euglycemic clamp resulted in activation of the PDH complex in both sedentary and trained rats, but the response of the PDH complex to the euglycemic clamp was significantly higher in trained rats (5.8%+/-0.5%) than in sedentary rats (2.9%+/-0.5%). These results suggest that exercise training promotes fatty acid oxidation in association with suppression of glucose oxidation in skeletal muscle under resting conditions, but increases the rate of carbohydrate oxidation when glucose flux into muscle cells is stimulated by insulin.

Animals↗
PubMed1999

Cloning and sequencing of the chromosomal DNA and cDNA encoding the mitochondrial citrate synthase of Aspergillus niger WU-2223L.

The complementary DNA (cDNA) and chromosomal DNA encoding the citrate synthase (EC 4.1.3.7) gene (cit1) of Aspergillus niger WU-2223L, a citric acid-producing strain, were cloned. Synthetic oligonucleotide primers were designed according to the amino acid sequences of already known eukaryotic citrate synthases and the codon bias of A. niger genes. The 920-bp DNA fragment was amplified by polymerase chain reaction with these primers using chromosomal DNA of WU-2223L as a template, and was employed to screen a cDNA library of A. niger. One full-length cDNA clone was isolated and sequenced, within which an ORF of 1425 by encoding a protein of 475 as with a molecular weight of 52,153 Da was found. Its N-terminal region contains a typical mitochondrial-targeting motif. The predicted as sequence was 82, 68, and 65% homologous with the mitochondrial citrate synthases of Neurospora crassa, Saccharomyces cerevisiae, and pig, respectively, but it showed lower homology to bacterial citrate synthases. The full-length cDNA clone was used to screen a chromosomal library of A. niger WU-2223L, and a 7.5 kb-SalI fragment containing the corresponding chromosomal gene was isolated. Comparison of the chromosomal and cDNA sequences revealed that the cit1 gene is interrupted by six introns. In the chromosomal DNA, upstream of the coding region, a CT-rich region, but not the TATAAA or CAAT motifs, was found. Escherichia coli MOB150, a citrate synthase-deficient mutant showing a glutamate-requiring phenotype, was transformed with the plasmid pKAC-35S, which is the expression vector pKK223-3 containing the cDNA fragment encoding a putative mature protein of A. niger citrate synthase. The transformant harboring pKAC-35S showed citrate synthase activity and a glutamate-nonrequiring phenotype.

Journal Article↗
PubMed1999

Troglitazone improves insulin-stimulated glucose utilization associated with an increased muscle glycogen content in obese Zucker rats.

Recent studies have demonstrated that troglitazone has the capacity to improve insulin resistance. The present study was undertaken to determine the effect of troglitazone on in vivo insulin action, the activities of the pyruvate dehydrogenase (PDH) complex and 3-hydroxyacyl-CoA dehydrogenase (3-HADH) in muscle, and muscle GLUT-4 and glycogen content in obese and lean Zucker rats. Rats were fed a normal chow diet with and without troglitazone as a food admixture (0.2%) for 3 weeks. In vivo insulin action was measured by the sequential euglycemic clamp technique at two different insulin infusion rates (6 and 30 mU/kg BW/min). At the basal (fasting) state and after the clamp studies, the activities of PDH complex and 3-HADH, and the amounts of GLUT-4 and glycogen contained in the red gastrocnemius muscles were determined. Troglitazone treatment produced a significant rise in the metabolic clearance rate of glucose (MCR) during the 6-mU/kg BW/min insulin clamp study (19.5+/-3.9 vs 9.9+/-1.5 ml/kg BW/min, mean+/-SE, P<0.05) in obese rats, but not in lean rats. Troglitazone significantly increased the muscle glycogen content after the clamp study, compared to non-treated rats, in obese rats (9.9+/-0.5 vs 6.5+/-0.4 mg/g tissue, P<0.05) and has the tendency to increase the activity state of PDH complex in obese and lean rats at the fasting state. However, no effect of the drug on muscle GLUT-4 content was found. These results indicate that troglitazone may improve insulin sensitivity associated with increased muscle glycogen content.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1999

Relationship between insulin and blood pressure in Japanese obese subjects.

OBJECT: The association of obesity and hypertension is well recognized. However, the nature of the relationship between increased body weight and blood pressure (BP) elevation has remained obscure. PATIENTS AND METHODS: We evaluated BP, insulin sensitivity, insulin clearance and fasting plasma insulin concentration in 19 younger (over 40 years) and in 15 older (more than 40 years) obese subjects to determine the relationships between BP and other factors. Insulin sensitivity and clearance were determined with the euglycemic clamp technique. RESULTS: BP was not associated with insulin sensitivity although most of the subjects showed insulin resistance. In the younger obese group, a positive correlation between diastolic BP and body mass index (kg/m2) was found (r=0.740; p=0.043). In the older obese group, systolic and diastolic BP were correlated with fasting plasma insulin levels (r=0.705; p=0.003; r=0.574; p=0.025, respectively), and systolic BP was inversely correlated with insulin clearance (r=-0.715, p=0.003). CONCLUSION: These results suggest that insulin is an important factor in BP elevation in older obese subjects, but not in younger obese subjects.

Adolescent↗
PubMed1999

Water-sorption kinetics of dental polymeric resin under tensile stressing conditions.

Water sorption tests were conducted on unfilled poly(methyl methacrylate) samples in distilled water at 5, 37, and 60 degrees C under three different tensile stress ratios (sigma appl/sigma ys = 0%, 5%, and 10%). Each sample was placed in a modified Hoffman open-side tubing clamp and subjected to four-point bending at pre-determined stress level for 1 day, 3 days, 1 week, 2 weeks, and 4 weeks. Water sorption was measured by weight change calculations, without accounting for any weight loss due to solubility of uncured monomer. A generalized diffusion equation can be used to express both stress-free and stress conditions; D = D0exp[-E (sigma)/kT]. It was found that the activation energy for water sorption diffusion was linearly related to applied stress ratios; i.e., E = 1.15 sigma appl/sigma ys + 10.76 (kJ/mol), with the correlation coefficient r = 0.97. Since the proportional pre-exponential constant, D0, is independent of temperature, it is speculated that the loading percentage of reinforcing filler elements in composite resin materials can be related to this constant.

Biocompatible Materials↗
PubMed1999

Effect of alpha/gamma phase ratio on corrosion behavior of dual-phase stainless steels.

Dual-phase stainless steels have been developed in order to reduce the nickel content, which is potentially responsible to an allergic reaction when these steels are used as medical or dental applications. In this study, two different dual-phase stainless steels (2205 and Z100) were electrochemically tested to evaluate their corrosion resistance in three corrosive solutions (i.e., synthetic saliva, 0.9% NaCl solution, and Ringer solution). Particularly, an attempt was made to correlate the corrosion resistance to a metallographic parameter, which is, in this study, the alpha/gamma phase ratio. It was concluded that (1) type 2205 stainless steel exhibited excellent corrosion resistance in all three corrosion media; however 2205 stainless steel decreases its corrosion resistance by increasing chloride concentration in tested electrolytes from synthetic saliva through 0.9% NaCl solution to Ringer solution. (2) X-ray diffraction analysis indicated that the alpha/gamma phase ratio of 2205 (1.735) was higher than that of Z100 (0.905). As a result, it is suggested that by increasing the alpha/gamma phase ratio the material shows more corrosion-prone behavior when being subjected to a hostile environment containing higher chloride ion concentration.

Chemical Phenomena↗
PubMed1998

Effect of insulin on intramuscular 3-hydroxybutyrate levels in diabetic rats.

It has been shown that inhibition of lipolysis and ketogenesis by insulin is more sensitive than suppression of hepatic glucose production and stimulation of tissue glucose uptake. Clinically, on the other hand, blood glucose concentrations fall much more quickly than blood ketone concentrations. Therefore, during continuous insulin infusion at a rate of 3.0 mU/kg B.W./min over a period of 150 min we monitored blood glucose and 3-hydroxybutyrate (3-OHBA) concentrations and muscle 3-OHBA levels using the microdialysis technique in streptozotocin-induced diabetic rats. Blood glucose concentrations decreased rapidly after insulin infusion. However, significant reduction in blood-3-OHBA concentration was found for the last 30 min. In muscle dialysate 3-OHBA concentrations and muscle local blood flow there was no significant change throughout the study. These results suggest that one possible mechanism of delayed improvement in ketonemia is a reduction in muscle removal capacity.

3-Hydroxybutyric Acid↗
PubMed1998

The association of physical activity level characteristics and other lifestyles with obesity in Nagoya University alumni, Japan.

Improving daily-life habits is considered to be effective in treating obesity. We have examined obesity in regular physical examinations in university students since 1974. In this study, the subjects were 199 students regarded as obese (Broca's index: more than 120%) and 326 non-obese students randomly selected (525 subjects in total) among students who underwent regular physical examinations at Nagoya University, Japan, between 1974 and 1978. Here we report our follow-up survey of obese university students and non-obese individuals who were students of the same university during the same period. This study was carried out for the purpose of clarifying the relationship between changes in lifestyle and body weight 20 years after graduation. Concerning eating behavior, a higher proportion of subjects cared about diet intake in the current non-obese group than in the current obese group (P<0.05). The meal-time in the obese was shorter than that in the non-obese group (P<0.01). Ten percent of subjects in the obese group and 24.4% of subjects in the non-obese group selected class II (moderate) or higher as indicative of the intensity of their daily physical activity. There was a significant difference in distribution between the groups (P<0.05). In the group showing improvement in obesity over time, a higher proportion of subjects cared about diet intake than in the group with continued obesity (P<0.05). Concerning intensity of physical activity, 11.8% of subjects in the group with continued obesity selected class II (moderate) or higher, while 45.5% of subjects in the group showing improvement in obesity chose class II (moderate) or higher. A significant difference in distribution existed between the groups (P<0.01). These findings suggest that the eating behavior of ending meals before feeling satiety and a lifestyle change to enhance the intensity of daily physical activity including walking, even if not having any special sports habits, are effective in decreasing body weight.

Adult↗