Search PubMed⌕ Search

Biomedical subjects

K Fujii

Publications and source records attributed to K Fujii.

At least 163 records · Page 9Linked to original sources
PubMed2000

Profile of a nonylphenol-degrading microflora and its potential for bioremedial applications.

Nonylphenol (NP) is an important intermediate in the production of various commercial and industrial materials, but is also known as a ubiquitous pollutant in urban aquatic environments. We recently studied the NP-degrading activities of microflora in several aquatic environments, and found a notable degrading activity for wastewater from a sewage treatment plant in Tokyo. This result led us to isolate NP-degrading microbes and identify biodegradation products. Using conventional plate culture techniques and molecular biological methods, Pseudomonas and Sphingomonas species, which are known for their degradation activities of many aromatic compounds, have been isolated. But it has also been found that Sphingomonas sp. (S-strain) is necessary and sufficient for the degradation of NP. Although the role of Pseudomonas sp. (P-strain) remains unclear, P-strain seems to provide some co-nutrients for the growth of S-strain. The degradation products were analyzed by GC/MS and NMR. More than 95% of NP was degraded within 10 days and aromatic compounds other than NP were not found, suggesting that the phenolic part of NP was completely degraded. We also examined the potential of S-strain for bioremedial applications. S-strain cells immobilized on chitosan or alginate beads retain their NP-degrading activity in flask-scale experiments. Furthermore, the chitosan-bound cells in a lab-scale bioreactor have been found to be persistent for repeated use, suggesting that S-strain is applicable to the treatment of NP-contaminated wastewater.

Base Sequence↗
PubMed2000

Calcium concentration in hepatocytes during liver ischaemia-reperfusion injury and the effects of diltiazem and citrate on perfused rat liver.

OBJECTIVE: To clarify the role of the calcium concentration in hepatocytes in liver ischaemia-reperfusion injury in relation to the protective effect of calcium-related agents. DESIGN: Serial calcium concentrations of extramitochondrial cytosolic sites (EMCa) and in mitochondria (MCa) in hepatocytes of isolated perfused rat liver were measured by an electron probe X-ray microanalyser, and the effects of calcium-related agents were evaluated. METHODS: Ischaemia was induced for 2 h, followed by 2 h of reperfusion in group I (without drug), group II (with diltiazem, 9.3 microM) and group III (with citrate, 5 mM). RESULTS: In group I, EMCa increased rapidly after reperfusion (before ischaemia, 2.0 mmol/kg wet weight; 1 min after reperfusion, 4.4 mmol/kg), and MCa increased (before ischaemia, 2.6 mmol/kg; 1 min after reperfusion, 5.07 mmol/kg). Thereafter the levels decreased, but remained high at 120 min after reperfusion in group I (EMCa, 3.2 mmol/kg, MCa 4.1 mmol/kg). At 1 min after reperfusion, EMCa in group III (2.9 mmol/kg) and MCa in groups II (3.4 mmol/kg) and III (4.0 mmol/kg) were significantly lower than in group I. At 120 min after reperfusion, the EMCa and MCa in groups II (2.5 and 3.1 mmol/kg, respectively) and III (2.4 and 3.0 mmol/kg, respectively) remained at significantly lower levels. Mitochondrial function in groups II and III was better preserved than in group I. The levels of hepatic enzymes in the perfused fluid of group III were lower than in group I. CONCLUSIONS: Calcium concentration in hepatocytes may play an important role in ischaemia-reperfusion injury. Diltiazem and citrate demonstrated a protective effect by maintaining a low calcium level in hepatocytes.

Adenosine Triphosphate↗
PubMed2000

Chemopreventive effect of curcumin on N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats.

Modifying effects of curcumin (derived from the rhizome of Curcuma longa L.) during the initiation or post-initiation phase of N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis were investigated in male F344 rats. Five-week-old rats were divided into 5 groups, and groups 1, 2 and 3 were given intraperitoneal injections of NMBA (0.5 mg / kg body weight / injection 15 times) for 5 weeks from 7 weeks old to induce esophageal neoplasms. Groups 2 and 3 were fed the diet containing 500 ppm curcumin during the initiation and post-initiation phases, respectively. Group 4 was given the diet containing curcumin throughout the experiment, and group 5 was kept on the basal diet alone and served as an untreated control. Incidence and multiplicity of esophageal neoplasms of group 1 (NMBA alone) were 66.7% and 0.83 +/- 0.70, respectively. Those of groups 2 and 3 were significantly less than those of group 1 (39.3%, 0.46 +/- 0.64, P < 0.05; 33.3%, 0.36 +/- 0.56, P < 0.05, respectively). Furthermore, the incidence and multiplicity of esophageal preneoplastic lesions (moderate or severe epithelial dysplasia) of group 2 (57.1%, 0.61 +/- 0.57; 40%, 0.29 +/- 0.46) or 3 (56.7%, 0.67 +/- 0.66; 23.3%, 0.23 +/- 0.43) were less than those of group 1 (100%, 1.67 +/- 0.70; 70.8%, 0.92 +/- 0.72) (P < 0.05). In this experiment, feeding of curcumin significantly decreased the expression of cell proliferation biomarkers (5-bromo-2'-deoxyuridine labeling index) in the non-lesional esophageal epithelium (P < 0.01). These findings indicate that curcumin inhibits NMBA-induced esophageal carcinogenesis when given during the post initiation as well as initiation phase. This inhibition may be related to suppression of the increased cell proliferation induced by NMBA in the esophageal epithelium.

Animals↗
PubMed2000

The Epstein-Barr virus pol catalytic subunit physically interacts with the BBLF4-BSLF1-BBLF2/3 complex.

The Epstein-Barr virus (EBV)-encoded replication proteins that account for the basic reactions at the replication fork are thought to be the EBV Pol holoenzyme, consisting of the BALF5 Pol catalytic and the BMRF1 Pol accessory subunits, the putative helicase-primase complex, comprising the BBLF4, BSLF1, and BBLF2/3 proteins, and the BALF2 single-stranded DNA-binding protein. Immunoprecipitation analyses using anti-BSLF1 or anti-BBLF2/3 protein-specific antibody with clarified lysates of B95-8 cells in a viral productive cycle suggested that the EBV Pol holoenzyme physically interacts with the BBLF4-BSLF1-BBLF2/3 complex to form a large complex. Although the complex was stable in 500 mM NaCl and 1% NP-40, the BALF5 protein became dissociated in the presence of 0.1% sodium dodecyl sulfate. Experiments using lysates from insect cells superinfected with combinations of recombinant baculoviruses capable of expressing each of viral replication proteins showed that not the BMRF1 Pol accessory subunit but rather the BALF5 Pol catalytic subunit directly interacts with the BBLF4-BSLF1-BBLF2/3 complex. Furthermore, double infection with pairs of recombinant viruses revealed that each component of the BBLF4-BSLF1-BBLF2/3 complex makes contact with the BALF5 Pol catalytic subunit. The interactions of the EBV DNA polymerase with the EBV putative helicase-primase complex warrant particular attention because they are thought to coordinate leading- and lagging-strand DNA synthesis at the replication fork.

Animals↗
PubMed2000

Sympathetic control of arterial membrane potential by ATP-sensitive K(+)-channels.

Stimulation of perivascular nerve terminals leads to a release of various neurotransmitters such as norepinephrine, epinephrine, acetylcholine, nitric oxide, and calcitonin gene-related peptide (CGRP). Because some of these substances have been shown to cause smooth muscle hyperpolarization by direct or endothelium-dependent mechanisms, we hypothesized that the liberation of 1 or more of these transmitters may lead to neurogenic hyperpolarization in arterial muscle cells. The present study was designed to determine the presence or absence of neurogenic hyperpolarization and, if present, its underlying mechanisms in isolated rat mesenteric resistance arteries, through the use of conventional microelectrode techniques. The experiments were performed under the combined blockade of alpha-adrenoceptors and purinoceptors with phentolamine and suramin to eliminate depolarizing responses to nerve stimulation. Under these conditions, perivascular nerve stimulation (5 Hz, 30 seconds) evoked smooth muscle hyperpolarization (-3.3+/-0.3 mV, n=15), which was abolished by tetrodotoxin, indicating the neurogenic origin of the response. This neurogenic hyperpolarization was resistant to atropine, nitro-L-arginine, or CGRP8-37, a CGRP antagonist, but was abolished by guanethidine and beta-blocker propranolol. This hyperpolarization was also abolished by glibenclamide, an ATP-sensitive K(+) channel (K(ATP)) blocker, but was unaffected by apamin, a Ca(2+)-activated K(+) channel blocker. In separate experiments, exogenous norepinephrine caused glibenclamide-sensitive hyperpolarization in the presence of phentolamine. On the other hand, norepinephrine-induced depolarization in the absence of phentolamine was enhanced by propranolol. These findings suggest that neurally released catecholamines cause membrane hyperpolarization through the activation of K(ATP) by beta-adrenoceptors. Such hyperpolarization may play an important role in the control of arterial membrane potential by opposing alpha-adrenergic depolarization.

Adenosine Triphosphate↗
PubMed2000

Renin-angiotensin system blockade improves endothelial dysfunction in hypertension.

Angiotensin-converting enzyme (ACE) inhibitor improves the impaired hyperpolarization and relaxation to acetylcholine (ACh) via endothelium-derived hyperpolarizing factor (EDHF) in arteries of spontaneously hypertensive rats (SHR). We tested whether the angiotensin type 1 (AT(1)) receptor antagonist also improves EDHF-mediated responses and whether the combined AT(1) receptor blockade and ACE inhibition exert any additional effects. SHR were treated with either AT(1) receptor antagonist TCV-116 (5 mg. kg(-1). d(-1)) (SHR-T), enalapril (40 mg. kg(-1). d(-1)) (SHR-E), or their combination (SHR-T&E) from 8 to 11 months of age. Age-matched, untreated SHR (SHR-C) and Wistar Kyoto (WKY) rats served as controls (n=8 to 12 in each group). Three treatments lowered blood pressure comparably. EDHF-mediated hyperpolarization to ACh in mesenteric arteries in the absence or presence of norepinephrine was significantly improved in all treated SHR. In addition, the hyperpolarization in the presence of norepinephrine was significantly greater in SHR-T&E than in SHR-E (ACh 10(-5) mol/L with norepinephrine: SHR-C -7; SHR-T -19; SHR-E -15; SHR-T&E -22; WKY -14 mV). EDHF-mediated relaxation, assessed in the presence of indomethacin and N:(G)-nitro-L-arginine, was markedly improved in all treated SHR. Hyperpolarization and relaxation to levcromakalim, a direct opener of ATP-sensitive K(+)-channel, were similar in all groups. These findings suggest that AT(1) receptor antagonists are as effective as ACE inhibitors in improving EDHF-mediated responses in SHR. The beneficial effects of the combined AT(1) receptor blockade and ACE inhibition appears to be for the most part similar to those of each intervention.

Acetylcholine↗
PubMed2000

Angiotensin-converting enzyme inhibitor prevents age-related endothelial dysfunction.

Vascular relaxation via endothelium-derived hyperpolarizing factor (EDHF) declines in association with aging and also with hypertension, and antihypertensive treatment improves the endothelial dysfunction connected with hypertension. We tested whether the angiotensin-converting enzyme inhibitor improves EDHF-mediated responses in normotensive rats, with special reference to the age-related process. Wistar-Kyoto rats (WKY) were treated with either 20 mg. kg(-1). d(-1) enalapril (WKY-E group) or a combination of 50 mg. kg(-1). d(-1) hydralazine and 7.5 mg. kg(-1). d(-1) hydrochlorothiazide (WKY-H group) from 9 to 12 months of age. Twelve-month-old WKY (WKY-O) and 3-month-old WKY (WKY-Y) served as controls (n=6 to 10 in each group). The 2 treatments lowered systolic blood pressure comparably. EDHF-mediated hyperpolarization to acetylcholine (ACh) in mesenteric arteries was significantly improved in WKY-E, but not in WKY-H, compared with WKY-O, and the hyperpolarization in WKY-E was comparable to that in WKY-Y (hyperpolarization to 10(-)(5) mol/L ACh in the presence of norepinephrine: WKY-O, -14+/-2 mV; WKY-E, -22+/-3 mV; WKY-H, -15+/-2 mV; and WKY-Y, -28+/-0 mV). EDHF-mediated relaxation, as assessed by relaxation to ACh in norepinephrine-precontracted rings in the presence of indomethacin and NO synthase inhibitor, was also significantly improved in WKY-E, but not in WKY-H, to a level comparable to that in WKY-Y (maximum relaxation: WKY-O, 45+/-6%; WKY-E, 63+/-8%; WKY-H, 43+/-4%; and WKY-Y, 72+/-4%). Hyperpolarization and relaxation to levcromakalim, an ATP-sensitive K(+) channel opener, were similar in all groups. These findings suggest that the angiotensin-converting enzyme inhibitor prevents the age-related decline in EDHF-mediated hyperpolarization and relaxation in normotensive rats, presumably through an inhibition of the renin-angiotensin system.

Acetylcholine↗
PubMed2000

Human bronchial intraepithelial T lymphocytes as a distinct T-cell subset: their long-term survival in SCID-Hu chimeras.

Intestinal intraepithelial T lymphocytes (i-IELs) show features different from those of conventional T cells and play specific roles in the mucosal immunity. To investigate whether human bronchial intraepithelial T lymphocytes (IELs) are a distinct entity, we examined T cells in human bronchial xenografts transplanted on mice with severe combined immune deficiency (SCID). We transplanted human bronchi subcutaneously into mice with SCID, resected the xenografts after various incubation periods (7-174 d), and examined them for CD3(+), CD4(+), CD8(+), and CD45(+) cells by immunohistochemistry. The number of CD3(+) cells in the lamina propria decreased significantly in the first month (from 308.7 +/- 60.2 to 70.9 +/- 49. 4/mm(2); P < 0.05), and xenografts more than 5 mo of age had scant T cells in the lamina propria (5.2 +/- 2.0/mm(2)). However, there was no significant difference between the number of CD3(+) IELs in freshly isolated bronchi and in xenografts maintained for more than 5 mo. In freshly isolated bronchi, the number of CD4(+) IELs was significantly lower than that of CD8(+) cells (2.35 +/- 0.62 versus 4.56 +/- 1.32/mm basement membrane; P < 0.01). After transplantation, the mean CD4-to-CD8 ratio of all xenografts was significantly higher than that of freshly isolated bronchi (5.2 +/- 0.9 versus 0.6 +/- 0.2; P < 0.005). The IELs were positive for CD45, which is specific for human leukocytes, and they were eliminated by irradiation before the transplantation. Almost all IELs (99.5%) in the xenografts expressed alphabeta T-cell receptor, and 35.8% of IELs expressed alpha(e)beta7 integrin. Bronchial epithelial cells in the xenografts expressed interleukin (IL)-7, stem cell factor, intercellular adhesion molecule (ICAM)-1, and human leukocyte antigen-DR (HLA-DR). We conclude that in the SCID-Hu chimera model, human bronchial IELs survive for more than 5 mo, unlike the T cells in the lamina propria, and we suggest that human bronchial IELs may be stimulated by bronchial epithelial cells expressing IL-7, stem cell factor, ICAM-1, and HLA-DR.

Animals↗
PubMed2000

Identification of novel human GH-1 gene polymorphisms that are associated with growth hormone secretion and height.

Height, which is partially determined by GH secretion, is genetically influenced. The purpose of this study was to identify polymorphisms in the GH-1 gene, which are associated with altered GH production. The subjects included prepubertal short children with GH insufficiency without gross pituitary abnormalities (n = 43), short children with normal GH secretion (n = 46), and normal adults (n = 294). A polymorphism in intron 4 (P-1, A or T at base 1663) was identified. Two additional polymorphic sites (P-2, T or G at base 218, and P-3, G or T at base 439) in the promoter region of the GH-1 gene were also identified and matched with the P-1 polymorphism (A or T, respectively) in more than 90% of the subjects. P-1, P-2, and P-3 were considered to be associated with GH production, and the results of P-2 are explained as a representative in this abstract. For example, the allele frequency of T at P-2 in prepubertal short children with GH insufficiency without gross pituitary abnormalities (58.1%) was significantly different from that in short children with normal GH secretion and normal adults (37.0% and 43.5%, respectively; P < 0.001). Furthermore, significant differences were observed in maximal GH peaks in provocative tests (11.1 vs. 18.2 ng/mL, P = 0.006), insulin-like growth factor I SD scores (SDS) (-2.4 vs. -0.8, P < 0.0001), and height (Ht) SDS (-3.7 vs. -3.0, P = 0/001) in children with the T/T or G/G genotypes at P-2, respectively. In the entire study group, significant differences in insulin-like growth factor SDS (T/T, -0.9; G/G, -0.2; P = 0.0009) and Ht SDS (T/T, -1.0; G/G, -0.4; P = 0.022) were observed between the T/T and G/G genotypes at P-2. These data indicate that GH secretion is partially determined by polymorphisms in the GH-1 gene, which explain some of the variations in GH secretion and Ht.

Adult↗
PubMed2000

Rapid detection of CYP2C18 genotypes by real-time fluorescence polymerase chain reaction.

In man, CYP2C19, a liver enzyme, plays an important role in the metabolism of several drugs. Mutation of the CYP2C19 gene results in a poor metaboliser phenotype. S-Mephenytoin hydroxylation genetic polymorphism is due to two mutations of the CYP2C19 gene, namely CYP2C19*2, located in exon 5, and CYP2C19*3, located in exon 4. CYP2C18 is also polymorphically expressed. The mutant alleles of this enzyme are CYP2C18m1, located in exon 2 and CYP2C18m2, located in the 5'-flanking region. We have developed an allele-specific TaqMan polymerase chain reaction (PCR) assay with which to detect CYP2C18 mutant alleles. This assay combines hybridization of the TaqMan probe and allele-specific amplification primers to the target DNA. The TaqMan probe is labelled with 6-carboxyfluorescein at the 5' end and 6-carboxytetramethylrhodamine together with a phosphate at the 3' end. Genotypes are separated according to the different threshold cycles of the wild type and mutant primers. We applied this procedure to DNA extracted from the blood or saliva of 144 healthy Japanese volunteers. The wt/wt, wt/m1, wt/m2, m1/m1, m1/m2 and m2/m2 genotypes of the CYP2C18 alleles detected by the assay were consistent with the results obtained from restriction enzyme cleavage. In accordance with a previous report, the genotypes of CYP2C18m1 and CYP2C18m2 coincided with those of CYP2C19*3 and CYP2C19*2, respectively. Therefore, detection of CYP2C18 mutant alleles also allows that of CYP2C19 mutant alleles. Among 19 poor metabolisers, eight showed the homozygous CYP2C19*2/CYP2C19*2, two the homozygous CYP2C19*3/CYP2C19*3 and nine the compound heterozygous CYP2C19*2/CYP2C19*3 genotype. We found the allele-specific TaqMan PCR assay rapid, simple and cost-effective, as well as suitable for high-throughput applications in a routine laboratory. This assay allows the fast and reliable detection of inherited disorders that might influence diagnosis and treatment.

Aryl Hydrocarbon Hydroxylases↗
PubMed2000

Voltage-dependent Ca2+ channels in resistance arteries from Dahl salt-sensitive rats.

To determine whether chronic salt-loading would alter voltage-dependent Ca2+ channels in resistance arteries of Dahl salt-sensitive rats, whole-cell voltage-clamp experiments were performed on single cells that were isolated from small mesenteric arteries. Dahl salt-sensitive rats were fed either an 8% NaCl diet (high-NaCl group) or a 0.3% NaCl diet (low-NaCl group) from the age of 6 or 7 weeks. After 4 to 5 weeks, systolic blood pressure was significantly higher in the high-NaCl group than in the low-NaCl group. In the high-NaCl group, the threshold potential for Ca2+ channel current was more negative and the current amplitude that was normalized by cell capacitance was higher at negative command potentials (-40 mV to -20 mV), as compared with the low-NaCl group. When the current was separated into fast transient current and slow sustained (L-type) current, the alteration in the high-NaCl group was attributable to the change in L-type current. The steady-state inactivation curve was not different between the high-NaCl and low-NaCl groups. In conclusion, L-type Ca2+ channels in resistance arteries of Dahl salt-sensitive rats became more available for opening near the resting potential after dietary salt-loading.

Animals↗
PubMed2000

Medical dissolution of struvite nephrolithiasis using amino acid preparation in dogs.

A new chemolytic therapy with amino acid preparation was tried for use on struvite renal stones in two dogs, which were admitted to Azabu University Veterinary Teaching Hospital. No other special diet, for the purpose of dissolving the stones, was fed during the treatment. Dissolution of the stones began at week 1, and no stone was detected on radiography at week 4 in both cases. The amino acid preparation thereafter has been administered every 2-3 days to prevent formation of the stones. After 6 months from treatment, complete dissolution was confirmed, and no relapse has been observed. Therefore, it is concluded that chemolytic therapy with amino acid preparation might be useful for the treatment of nephrolithiasis with struvite renal stones in dogs.

Animals↗
PubMed2000

Intercellular adhesion molecule 1 discriminates functionally different populations of human osteoblasts: characteristic involvement of cell cycle regulators.

The concept of differential regulation of certain adhesion molecules on different cell subsets and their relevance to cell functions has emerged in recent years. The initial event in bone remodeling is an increase in osteoclastic bone resorption and cell adhesion between osteoclastic precursors and bone marrow stromal cells or osteoblasts is known to commit the osteoclast development. Here, we show that human osteoblasts can be divided into two subsets based on the expression of the intercellular adhesion molecule (ICAM)-1; ICAM-1+ osteoblasts highly adhered to monocytes, including osteoclast precursors, produced osteoclast differentiation factor (ODF), and induced multinuclear osteoclast-like cell formation. Anti-ODF monoclonal antibody (mAb) did not inhibit the adhesion of monocytes to osteoblastic cells, whereas anti-leukocyte function-associated antigen (LFA)-1, a receptor for ICAM-1, mAb blocked the adhesion. We thereby propose that the higher affinity adhesion via LFA-1/ICAM-1 is prerequisite for efficient function of membrane-bound ODF during osteoclast maturation. The functional characteristics of ICAM-1+ osteoblasts were emphasized further by cell cycle regulation, as manifested by (i) up-regulation of p53 and p21, (ii) reduction of activity of cyclin-dependent kinase (cdk) 6, (iii) underphosphorylation of retinoblastoma protein, (iv) increased Fas but reduced bcl-2 expression, and (v) majority of cells remained at G0/G1 phase. Furthermore, ICAM-1+ osteoblasts were induced by interleukin-1beta (IL-1beta). Taken together, we propose that the differentiation of osteoblasts to ICAM-1+ subpopulation by inflammatory cytokines plays an important role in osteoporosis, which is observed in patients with chronic inflammation, because ICAM-1+ osteoblasts can bias bone turnover to bone resorption, committing osteoclast maturation through cell adhesion with its precursor, and the majority of ICAM-1+ osteoblasts arrested at G0/G1 phase. Such regulation of cell cycle arrest also is an important determinant of the life span of cells in bone in which continuous bone remodeling maintains its homeostasis.

Carrier Proteins↗
PubMed2000

Clinical cure of glioblastoma--two case reports.

We report two cases of "decade survivor" of glioblastoma. Case 1 is a 34-year-old female who developed a tumor in the left frontal pole, and Case 2 is a 46-year-old male with a left frontal tumor. Both tumors were surgically excised and the patients received postoperative chemo-radiotherapy. Histological re-evaluation of the resected tumor tissue confirmed the most malignant type of glioma-glioblastoma. We speculate that the entire extent of tumors had been extirpated by surgery in both cases.

Adult↗
PubMed2000

Solitary fibrous tumor arising from the falx cerebri--case report.

A 50-year-old female was admitted with headache and visual disturbance. Neuroimaging demonstrated a well-demarcated large tumor attached to the falx cerebri. The tumor was totally removed by surgery. Histological examination showed that the tumor consisted of spindle cells with no pattern in the collagenous background. Staghorn-like blood vessels were common. Immunohistochemical study showed the tumor cells were strongly positive for CD34 and vimentin, but negative for epithelial membrane antigen. The diagnosis was solitary fibrous tumor arising from the falx cerebri. Solitary fibrous tumor is rare within the cranial cavity, and can be distinguished from meningioma and hemangiopericytoma by the histological, ultrastructural, and immunohistochemical findings.

Brain Neoplasms↗
PubMed2000

Adding silanes to MMA: the effects on the water absorption, adhesive strength and mechanical properties of acrylic denture base resins.

The adhesive strength of porcelain artificial teeth and polymethylmethacrylates (PMMAs), which contained silanes with various number of vinyl or ethoxy groups, and the mechanical and physical properties of the PMMAs were measured. Four types of PMMAs with silanes showed high adhesive shear strength and caused fractures in the porcelain. Water absorption of the PMMAs increased with the addition of silane, but that of one type with silane was almost the same as the PMMA only type. The flexural strengths of the PMMAs with silane, except for one type, showed no significant differences compared with that of PMMA (p < 0.05). The Tg levels of all PMMAs with silane fell less than that of PMMA. From these results, it was found that PMMA with silane from three vinyl groups and one ethoxy group showed excellent chemical bonding to porcelain and low water absorption.

Absorption↗
PubMed2000

A method for evaluating color stability of light-cured composite resins using an experimental filter.

The purpose of this study was to investigate a method for evaluating color stability of light-cured composite resins using an experimental filter that simulates human enamel. The light transmission coefficients and their spectral distributions from 400 to 600 nm of twelve enamel specimens were measured. The experimental filter was designed so that its light transmittance characteristics were similar to those of enamel. Color stability tests for ten shades of two light-cured composite resins, which were irradiated directly and indirectly through the experimental filter with a light source, were performed. Despite different irradiation procedures, most materials exhibited significant color changes in the color stability test. Although the differences were small, the group of specimens irradiated indirectly through the filter showed significantly higher color differences in comparison with those irradiated directly. Our results indicate that the light attenuating effect of enamel affects the color stability of light-cured composite resins.

Color↗