PubMed Health⌕ Search

Biomedical subjects

T Yoneyama

Publications and source records attributed to T Yoneyama.

At least 19 recordsLinked to original sources
PubMed2006

Early CT signs in patients with acute middle cerebral artery occlusion: incidence of contrast staining and haemorrhagic transformations after intra-arterial reperfusion therapy.

AIM: To investigate how often early computed tomography (CT) signs are associated with blood-brain barrier (BBB) disruption and result in haemorrhagic transformations. MATERIALS AND METHODS: Serial CT findings were prospectively evaluated in 61 patients with acute middle cerebral artery (MCA) occlusion who underwent initial CT examination within 3h of stroke onset and who were treated with intra-arterial reperfusion therapy within 6h of stroke onset. Obscuration of the margin of the lentiform nucleus and loss of the insular ribbon were evaluated as early CT signs in the deep MCA territories. Cortical effacement was also evaluated. BBB disruption was defined as contrast medium staining in post-therapeutic CT just after reperfusion therapy. The relationship between pre-therapeutic early CT signs and post-therapeutic contrast staining or haemorrhagic transformations was investigated. RESULTS: The frequency of early CT signs in the deep MCA territories was significantly higher than that of cortical effacement (68.9 versus 27.9%). There were significant correlations between pre-therapeutic early CT signs and post-therapeutic contrast staining in both the deep and superficial MCA territories. Compared with early CT signs in the deep MCA territories, cortical effacement had a significantly higher incidence of post-therapeutic contrast staining (54.8 versus 82.4%). Although not statistically significant, cortical effacement tended to develop into haemorrhagic transformations. There was no correlation between early CT signs in the deep MCA territories and haemorrhagic transformations. CONCLUSION: Cortical effacement may be an advanced CT sign with BBB disruption and potential risk for haemorrhagic transformations. The presence of early CT signs in the deep MCA territories may not be a contraindication of reperfusion therapy.

Acute Disease↗
PubMed2006

Influence of phase transformation on the torsional and bending properties of nickel-titanium rotary endodontic instruments.

AIM: To investigate the relationship between the functional properties and the phase transformation of nickel-titanium endodontic instruments. METHODOLOGY: Five types of rotary nickel-titanium endodontic instruments with a 0.30 mm diameter tip (EndoWave, HERO 642, K3, ProFile.06, and ProTaper) were selected to investigate torsional and bending properties, and phase transformation behaviour. A torsional test was performed according to ISO publication 3630-1, and maximum torque and angular deflection at fracture were measured. Bending load of the instruments was measured in a cantilever-bending test at 37 degrees C with the maximum deflection of 4.0 mm. A stainless steel K-file was used for reference. Phase transformation behaviour was measured by differential scanning calorimetry (DSC). From the DSC curve, transformation temperatures were calculated. Data were analysed by anova and the Tukey-Kramer's test. RESULTS: The maximum torsional torque values of HERO, K3 and ProTaper were significantly higher (P < 0.05) than those of EndoWave, ProFile and K-file. The K-files had the lowest torque value. Angular deflection at fracture was significantly higher (P < 0.05) for K-files than that for any nickel-titanium instrument. The bending load values of HERO and K3 were significantly higher (P < 0.05) than those of EndoWave, ProFile, ProTaper and K-file. The K-files had the lowest load value, although residual deflection remained. The transformation temperatures of HERO and K3 were significantly lower (P < 0.05) than those of EndoWave, ProFile and ProTaper. CONCLUSIONS: The functional properties of nickel-titanium endodontic instruments, especially their flexible bending load level, were closely related to the transformation behaviour of the alloys.

Calorimetry, Differential Scanning↗
PubMed2004

Precision spectroscopy of pionic 1s states of Sn nuclei and evidence for partial restoration of chiral symmetry in the nuclear medium.

Deeply bound 1s states of pi(-) in (115,119,123)Sn were preferentially observed using the Sn(d,3He) pion-transfer reaction under the recoil-free condition. The 1s binding energies and widths were precisely determined and were used to deduce the isovector parameter of the s-wave pion-nucleus potential to be b1=-(0.115+/-0.007)m(-1)(pi). The observed enhancement of |b(1)| over the free piN value (b(free)1/b1=0.78+/-0.05) indicates a reduction of the chiral order parameter, f*pi(rho)2/f2pi approximately 0.64, at the normal nuclear density, rho=rho(0).

Journal Article↗
PubMed2003

Wear properties of Ti and Ti-6Al-7Nb castings for dental prostheses.

Titanium has been increasingly applied to dental prostheses because of its biocompatibility. However, application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the wear resistance of high-strength Ti-6Al-7Nb alloy castings for dental application. Test specimens were cast from commercially pure titanium (CP-Ti grades 2 and 3) and Ti-6Al-7Nb alloy ingots, and subjected to a wear test simulating the occlusal loading pattern. Wear resistance was evaluated by the weight loss during the test. Ti-6Al-7Nb alloy was found to exhibit lower weight loss than CP-Ti. Moreover, scanning electron microscopic (SEM) observation after the test revealed that the worn surface of Ti-6Al-7Nb alloy is much smoother than that of CP-Ti. These results indicate that Ti-6Al-7Nb alloy castings can be used to produce dental prostheses of improved wear resistance and mechanical strength.

Biomechanical Phenomena↗
PubMed2003

Adhesive bonding of super-elastic titanium-nickel alloy castings with a phosphate metal conditioner and an acrylic adhesive.

The purpose of the current study was to evaluate the bonding characteristics of super-elastic titanium-nickel (Ti-Ni) alloy castings. Disk specimens were cast from a Ti-Ni alloy (Ti-50.85Ni mol%) using an arc centrifugal casting machine. High-purity titanium and nickel specimens were also prepared as experimental references. The specimens were air-abraded with alumina, and bonded with an adhesive resin (Super-Bond C & B). A metal conditioner containing a phosphate monomer (Cesead II Opaque Primer) was also used for priming the specimens. Post-thermocycling average bond strengths (MPa) of the primed groups were 41.5 for Ti-Ni, 30.4 for Ti and 19.5 for Ni, whereas those of the unprimed groups were 21.6 for Ti, 19.3 for Ti-Ni and 9.3 for Ni. Application of the phosphate conditioner elevated the bond strengths of all alloy/metals (P < 0.05). X-ray fluorescence analysis revealed that nickel was attached to the debonded resin surface of the resin-to-nickel bonded specimen, indicating that corrosion of high-purity nickel occurred at the resin-nickel interface. Durable bonding to super-elastic Ti-Ni alloy castings can be achieved with a combination of a phosphate metal conditioner and a tri-n-butylborane-initiated adhesive resin.

Adhesives↗
PubMed2003

The changes of hepatic metallothionein synthesis and the hepatic damage induced by starvation in mice.

Metallothionein (MT) is induced in the liver not only by heavy metals, but also by stress such as starvation. However, the meaning of the induced MT during starvation has never been clear. In this study, we investigated the relationship between changes in hepatic MT synthesis and the hepatic damage that occurs during starvation. MT synthesis was assessed by measuring MT contents and the expression of the MT gene in the liver. The hepatic damage was assessed by measuring glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) activities in the serum. MT synthesis in the liver increased over the normal level by starvation, but decreased under the normal level by refeeding after starvation. Both GPT and GOT activities of the refeeding group were higher than those of the control group. However, MT synthesis increased by a subcutaneous injection with CdCl(2) (1 mg Cd /kg) at the same time as refeeding after starvation. At this point, GOT activity decreased until it reached the normal level. MT synthesis decreased by refeeding after starvation, and from the results found in this study, we proposed the hypothesis that the liver damage caused by refeeding after starvation might be due to the decrease in the synthesis of a sufficient amount of MT induced by metals.

Alanine Transaminase↗
PubMed2002

Deeply bound 1s and 2p pionic states in 205Pb and determination of the s-wave part of the pion-nucleus interaction.

We observed well-separated 1s and 2p pi(-) states in 205Pb in the 206Pb(d,3He) reaction at T(d) = 604.3 MeV. The binding energies and the widths determined are B(1s) = 6.762+/-0.061 MeV, Gamma(1s) = 0.764(+0.154)(-0.171) MeV, B(2p) = 5.110+/-0.045 MeV, and Gamma(2p) = 0.321(-0.062)(+0.060) MeV. They are used to deduce the real and imaginary strengths of the s-wave part of the pion-nucleus interaction, which translates into a positive mass shift of pi(-) in 205Pb.

Journal Article↗
PubMed2002

Bending properties of hollow super-elastic Ti-Ni alloy wires and compound wires with other wires inserted.

The purpose of this research was to investigate the possible orthodontic application of the hollow super-elastic Ti-Ni alloy wire, which was thought not only to deliver much lower and more continuous orthodontic force than conventional Ti-Ni wires, but also be able to be applied as a compound wire when combined with another wire. The examinations of bending properties were performed by the three-point bending test. The following results were obtained. 1. The hollow wire had lower load in the super-elastic range, smaller load-deflection rate and stress hysteresis in comparison with the conventional wire of the same diameter. 2. The load of the hollow wire was controllable by heat treatment. The stress hysteresis was further decreased by a two-step heat treatment. 3. The compound wire formed by inserting other types of wires into the hollow core exhibited changes in various bending properties such as increased load or load-deflection rate, according to the types and diameters of the inserted wire. The hollow wire delivers much lighter and more continuous orthodontic force, and, through heat treatment or deployment as a compound wire, it is possible to alter various bending properties. Therefore, this hollow wire was evaluated as a promising candidate for orthodontic application.

Journal Article↗
PubMed2002

Anisotropic orthodontic force from the hollow super-elastic Ti-Ni alloy wire by transforming the wire cross-section.

The purpose of this research was to devise a method for transforming the cross-section of the hollow super-elastic Ti-Ni alloy round wire and to examine the changes in its bending properties for clinical orthodontic application. The specimen wires were pressed with the use of heated pliers to transform the cross-sectional shape. As a result, transformation of the wire cross-section with super-elasticity was possible. As a verified by cantilever test and three-point bending test of the transformed specimens, a two-dimensional orthodontic force, which was different in each bending direction, was obtained. The hollow wire showed considerably high load level in the long axis along with markedly low load level in the short axis, which was mainly caused by the change in the moment of inertia by transforming the cross-section. It was revealed that, by transforming the wire cross-section of the hollow super-elastic Ti-Ni alloy round wires, anisotropic orthodontic force in bending properties could be obtained with super-elasticity.

Journal Article↗
PubMed2002

Bending property and phase transformation of Ti-Ni-Cu alloy dental castings for orthodontic application.

Bending property of Ti-Ni-Cu alloy castings was investigated in a three-point bending test for orthodontic application in relation to the phase transformation. The compositions of the alloys were Ti-50.8Ni and Ti-40.8Ni-10.0Cu (mol %), and four cross-sectional shapes of the specimens were selected. Heat treatment was performed at 713, 753 or 793 K for 1.8 ks. The bending load changed by the cross-sectional size and shape mainly because of the difference in the moment of inertia of area, but the load-deflection relation did not differ proportionally in the unloading process. The difference between the load values in the loading and the unloading processes was relatively small for Ti-Ni-Cu alloy. With respect to the residual deflection, there was no significant difference between Ti-Ni and Ti-Ni-Cu alloys with the same treatment condition. The load values in the loading and the unloading processes decreased by each heat treatment for Ti-Ni alloy; however, the decrease in the load values for Ti-Ni-Cu alloy was not distinct. It is proved that Ti-Ni-Cu alloy castings produce effective orthodontic force as well as stable low residual deflection, which is likely to be caused by the high and sharp thermal peaks during phase transformation.

Journal Article↗
PubMed2002

Effect of heat treatment with the mould on the super-elastic property of Ti-Ni alloy castings for dental application.

Tensile property of Ti-50.85Ni (mol %) alloy castings was investigated quantitatively in relation to the thermal behavior accompanied with phase transformation to evaluate the effect of heat treatment after casting with the mould in air. The heat treatment temperature was 713 or 773 K, and the period was 0.9, 1.8, or 3.6 ks. Apparent proof stress of the castings decreased with increasing period of heat treatment, and the decrease was larger with the treatment at 773 K. Residual strain also decreased by the heat treatment, however, it was low with the treatment for relatively short period, i.e. 713 K-0.9 and 1.8 ks, and 773 K-0.9 ks treatments. From the thermal behavior measured by differential scanning calorimetry (DSC), the ascent in the transformation temperatures and the increase in the thermal peak height appeared to influence the changes in the tensile property. These changes by heat treatment were believed to be effective to utilize more flexibility, less stress and less permanent deformation in dental castings.

Journal Article↗
PubMed2001

Albers-Schönberg disease (autosomal dominant osteopetrosis, type II) results from mutations in the ClCN7 chloride channel gene.

Albers-Schönberg disease, or autosomal dominant osteopetrosis, type II (ADO II), is the most common form of osteopetrosis, a group of conditions characterized by an increased skeletal mass due to impaired bone and cartilage resorption. Following the assignment of the gene causing ADO II to chromosome 16p13.3, we now report seven different mutations in the gene encoding the ClCN7 chloride channel in all 12 ADO II families analysed. Additionally, a patient with the severe, autosomal recessive, infantile form of osteopetrosis (ARO) was identified as being homozygous for a ClCN7 mutation. From genotype-phenotype correlations, it seems that ADO II reflects a dominant negative effect, whereas loss-of-function mutations in ClCN7 do not cause abnormalities in heterozygous individuals. Because some ARO patients have mutations in both copies of the ClCN7 gene, ADO II is allelic with a subset of ARO cases.

Alleles↗
PubMed2001

Genomewide-linkage and haplotype-association studies map intracranial aneurysm to chromosome 7q11.

Rupture of intracranial aneurysms (IAs) causes subarachnoid hemorrhage, a devastating condition with high morbidity and mortality. Angiographic and autopsy studies show that IA is a common disorder, with a prevalence of 3%-6%. Although IA has a substantial genetic component, little attention has been given to the genetic determinants. We report here a genomewide linkage study of IA in 104 Japanese affected sib pairs in which positive evidence of linkage on chromosomes 5q22-31 (maximum LOD score [MLS] 2.24), 7q11 (MLS 3.22), and 14q22 (MLS 2.31) were found. The best evidence of linkage is detected at D7S2472, in the vicinity of the elastin gene (ELN), a candidate gene for IA. Fourteen distinct single-nucleotide polymorphisms (SNPs) were identified in ELN, and no obvious allelic association between IA and each SNP was observed. The haplotype between the intron-20/intron-23 polymorphism of ELN is strongly associated with IA (P=3.81x10-6), and homozygous patients are at high risk (P=.002), with an odds ratio of 4.39. These findings suggest that a genetic locus for IA lies within or close to the ELN locus on chromosome 7.

3' Untranslated Regions↗
PubMed2001

Drug release from and mechanical properties of press-coated tablets with hydroxypropylmethylcellulose acetate succinate and plasticizers in the outer shell.

Dissolution profiles of diltiazem hydrochloride (DIL) contained in core tablets from press-coated (PC) tablets with hydroxypropylmethylcellulose acetate succinate (HPMCAS) and plasticizers-adsorbent in the outer shell were investigated. Although, on the addition of triethyl citrate (TEC), triacetin (TA), and acetyltriethy citrate (ATEC) as plasticizers, DIL release was suppressed completely in first fluid (pH 1.2) for 10 h, it was not suppressed in HPMCAS on the addition of dibutyl sebacate (DBS) and acetylated monoglyceride. On the other hand, DIL in second fluid (pH 6.8) was released rapidly after a lag time in all the PC tablets. Water-soluble plasticizers such as TEC, TA, and ATEC showed greater compatibility to HPMCAS, and the results were consistent with suppression of DIL release in first fluid. Furthermore, as to PC tablets with HPMCAS and TEC-adsorbent, the DIL release in second fluid did not change after pretreatment in first fluid by the paddle-beads methods. To evaluate the resistance of the outer shell against such a mechanical impact, tablets with HPMCAS, HPMCAS and TEC- or DBS-adsorbent (H, HT, or HD tablets, respectively) were prepared. In compressive load-strain curves after immersion in first fluid, wet crushing strength was lower in the order of HT > H > HD tablets. Also, the curves of HT tablets at 3 and 21 h after immersion were quite different from those of other tablets, and it was hard to find crushing points. These results suggested that the resistance of the outer shell was due to plastic deformation properties involving some interaction between HPMCAS and TEC.

Cardiovascular Agents↗
PubMed2001

GTP cyclohydrolase I feedback regulatory protein-dependent and -independent inhibitors of GTP cyclohydrolase I.

GTP cyclohydrolase I feedback regulatory protein (GFRP) mediates the feedback inhibition of GTP cyclohydrolase I activity by (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) through protein complex formation. Since guanine and BH4 have a common pyrimidine ring structure, we examined the inhibitory effect of guanine and its analogs on the enzyme activity. Guanine, 8-hydroxyguanine, 8-methylguanine, and 8-bromoguanine inhibited the enzyme activity in a GFRP-dependent and pH-dependent manner and induced complex formation between GTP cyclohydrolase I and GFRP. The type of inhibition by this group is a mixed type. All these properties were shared with BH4. In striking contrast, inhibition by 8-azaguanine and 8-mercaptoguanine was GFRP-independent and pH-independent. The type of inhibition by 8-azaguanine and 8-mercaptoguanine was a competitive type. The two compounds did not induce complex formation between the enzyme and GFRP. These results demonstrate that guanine compounds of the first group bind to the BH4-binding site of the GTP cyclohydrolase I/GFRP complex, whereas 8-azaguanine and 8-mercaptoguanine bind to the active site of the enzyme. Finally, the possible implications in Lesch-Nyhan syndrome and Parkinson diseases of the inhibition of GTP cyclohydrolase I by guanine and 8-hydroxyguanine are discussed.

Adjuvants, Immunologic↗
PubMed2001

Correlation between loose density and compactibility of granules prepared by various granulation methods.

The objectives of this study were to prepare the lactose granules by various granulation methods using polyethylene glycol 6000 (PEG 6000) as a binder and to evaluate the effects of granulation methods on the compressibility and compactibility of granules in tabletting. Lactose was granulated by seven granulation methods -- four wet granulations including wet massing granulation, wet high-speed mixer granulation, wet fluidized bed granulation and wet tumbling fluidized bed granulation; and three melt granulations including melt high-speed mixer granulation, melt fluidized bed granulation and melt tumbling fluidized bed granulation. The loose density, angle of repose, granule size distribution, mean diameter of granules, and the tensile strength and porosity of tablets were evaluated. The compactibilities of granules were varied by the granulation methods. However, the difference in compactibility of granules could not be explained due to the difference in compressibility, since there was no difference in Heckel plots due to granulation methods. Among their granule properties, the loose density of granules seemed to have a correlation with the tablet strength regardless of the granulation methods.

Chemistry, Pharmaceutical↗
PubMed2001

Catecholamines decrease nitric oxide production by cytokine-stimulated hepatocytes.

BACKGROUND: Catecholamines are significantly elevated in inflammatory responses and play a regulatory role in sepsis. Nitric oxide (NO), also a key inflammatory mediator in sepsis, is produced in large amounts by the inducible nitric oxide synthase (iNOS) in the liver. The purpose of this study was to test the hypothesis that catecholamines play a role in the regulation of NO production by hepatocytes. METHODS: Primary hepatocytes were isolated from healthy male Sprague-Dawley rats and either cultured with normal medium or stimulated with cytomix (interleukin-1 beta, interferon-gamma, and tumor necrosis factor-alpha) in the presence or absence of epinephrine or norepinephrine at varying concentrations. Total RNA was isolated 6 hours after treatment and analyzed by Northern blotting for iNOS mRNA. Protein extracts were obtained at 12 hours and were analyzed by Western immunoblotting for iNOS. Cell culture supernatants were analyzed for NO, determined as the stable end-product NO(2)(-), at 24 hours. RESULTS: Epinephrine and norepinephrine significantly decreased NO(2)(-) levels in stimulated hepatocytes but had no effect on iNOS mRNA or protein levels. The decrease in NO(2)(-) was reproduced by the adenylate cyclase stimulator, forskolin. The catecholamine-induced decrease in NO(2)(-) was completely reversed by the protein kinase A inhibitor Rp-8-Br-cyclic adenosine monophosphate. CONCLUSIONS: Catecholamines decrease hepatocyte production of NO in response to cytokine stimulation. This effect seems to be due to post-translational events and appears to be mediated in part by cyclic adenosine monophosphate.

8-Bromo Cyclic Adenosine Monophosphate↗