Search PubMed⌕ Search

Biomedical subjects

J Doi

Publications and source records attributed to J Doi.

At least 19 recordsLinked to original sources
PubMed2004

Effect of 2-hydroxyethyl methacrylate pre-treatment on micro-tensile bond strength of resin composite to demineralized dentin.

The purpose of this study was to evaluate the effect of 2-hydroxyethyl methacrylate (HEMA) application on the micro-tensile bond strength of resin composite to demineralized dentin. Artificially demineralized lesions were formed on bovine dentin surfaces and treated with 10, 30, 50, 70 and 100 wt% HEMA aqueous solution. The surfaces were then applied and covered with SE Bond and AP-X according to the manufacturer's instruction. After immersion in 37 degrees C water for 24 h, bond strength were measured using a universal testing machine. Bond strengths to both demineralized dentin and normal dentin, without HEMA application, were also measured. Scanning electron microscopic (SEM) observation and confocal laser scanning microscopy (CLSM) analysis at the resin-dentin interface were also performed. The bond strength data were statistically compared with anova and Scheffe's test (P < 0.05). Bond strength to demineralized dentin treated with over 30 wt% HEMA aqueous solution were significantly higher than that to demineralized dentin without HEMA application, but significantly lower than that to normal dentin. SEM observation revealed that the hybrid layer and resin-tags thickened and lengthened with HEMA application. In CLSM, the diffusion of adhesive primer into demineralized dentin increased with HEMA application. These results indicated that HEMA application might increase the bond strength to demineralized dentin by the enhancement of resin monomer penetration of HEMA.

Animals↗
PubMed2004

Micro-tensile bond strength of self-etching primer adhesive systems to human coronal carious dentin.

The aim of this study was to evaluate the micro-tensile bond strengths of three self-etching primer adhesive systems to normal dentin (ND), caries-affected dentin (CAD) and caries-infected dentin (CID). Human extracted molars with caries were used, and flat dentin surfaces ground by 600-grit SiC paper were prepared. The surfaces were dyed using Caries-Detector solution, treated with Clearfil SE Bond, Mac-Bond II and UniFil Bond, and then covered with resin composites according to manufacturer's instructions. After immersion in 37 degrees C water for 24 h, the teeth were serially sectioned into multiple slices. Each slice was distinguished into ND, CAD and CID groups by the degree of staining, and the bond strength was measured in a universal testing machine. Scanning electron microscopic (SEM) observation was also performed. For statistical analysis, anova and Scheffe's test were used (P < 0.05). The bond strengths of the three adhesive systems to CAD and CID were significantly lower than those to ND. There was significant difference in the bond strength to ND between Clearfil SE Bond and UniFil Bond, but no significant differences to CAD and CID among the three adhesive systems. On SEM, the hybrid layers in CAD and CID showed more porous structures compared with ND. The results indicated that the bond strengths to CAD and CID were not affected by a variety of self-etching primer adhesive systems because of the porous hybrid layer formation in carious dentin.

Dental Bonding↗
PubMed2002

Bonding of self-etch and total-etch adhesives to carious dentin.

Carious dentin is partially demineralized and contains mineral crystals in the tubules. This may permit the deeper etching of intertubular dentin but prevent resin tag formation during bonding. We hypothesize that resin adhesives will produce lower bond strengths to caries-infected and caries-affected dentin compared with normal dentin. We tested this by measuring the microtensile bond strength of a total-etch adhesive and an experimental self-etching adhesive (ABF) to caries-infected, caries-affected, and sound dentin and by correlating those results with ultrastructural observations. The bond strengths of both adhesives to sound dentin were significantly (p < 0.05) higher than those to caries-affected dentin, which, in turn were significantly (p < 0.05) higher than those to caries-infected dentin. For both adhesives, hybrid layers in caries-affected dentin were thicker but more porous than those in sound dentin. The lower bond strengths may be due to the lower tensile strength of caries-affected dentin. Clinically, this may not be a problem, since such lesions are normally surrounded by normal dentin or enamel.

Acid Etching, Dental↗
PubMed2001

Characterization of a proximal element in the rat preadipocyte factor-1 (Pref-1) gene promoter.

Preadipocyte factor-1 (Pref-1) was shown to negatively regulate adipocyte differentiation. We recently reported that ZOG, a rat homolog of Pref-1, was specifically expressed in the adrenal zona glomerulosa. Results of the investigation of Pref-1 expression in preadipocyte and in undifferentiated adrenal cortex suggested that down-regulation of Pref-1 gene was closely correlated with the differentiation process. In this study we demonstrate that an upstream region (from -76 to -47) of the rat Pref-1 gene was essential for its expression in adrenocortical carcinoma-derived H295R cells. A nucleotide sequence found in this region, GCGTGGGCGTGGGCGGGGG (Egr/GC-box), seemed to contain three elements, two early growth response (Egr) elements and one GC-box, overlapping each other. Mutations of four or five nucleotides in a 7-nucleotides-stretch in the midst of the Egr/GC-box eliminated the binding of Sp1/3, abolished the activation by Egr-factor(s) and diminished the Pref-1 promoter activity. When mutations were introduced into the outside of the middle portion, the binding of Sp1/3 to the Egr/GC-box was abolished similarly. However, the decrease in the promoter activity was less than that found with the construct mutated at the middle. These results indicated that an element present at the 7-nucleotides-stretch in the midst of the Egr/GC-box might be important for the Pref-1 promoter activity, and this proximal element was possibly activated by a still-unidentified nuclear factor(s). This element would function as the promoter of the Pref-1 gene in H295R cells, but not in HeLa cells.

Adipocytes↗
PubMed2001

Salt-inducible kinase is involved in the ACTH/cAMP-dependent protein kinase signaling in Y1 mouse adrenocortical tumor cells.

The involvement of salt-inducible kinase, a recently cloned protein serine/threonine kinase, in adrenal steroidogenesis was investigated. When Y1 mouse adrenocortical tumor cells were stimulated by ACTH, the cellular content of salt-inducible kinase mRNA, protein, and enzyme activity changed rapidly. Its level reached the highest point in 1-2 h and returned to the initial level after 8 h. The mRNA levels of cholesterol side-chain cleavage cytochrome P450 and steroidogenic acute regulatory protein, on the other hand, began to rise after a few hours, reaching the highest levels after 8 h. The salt-inducible kinase mRNA level in ACTH-, forskolin-, or 8-bromo-cAMP-treated Kin-7 cells, mutant Y1 with less cAMP-dependent PKA activity, remained low. However, Kin-7 cells, when transfected with a PKA expression vector, expressed salt-inducible kinase mRNA. Y1 cells that overexpressed salt-inducible kinase were isolated, and the mRNA levels of steroidogenic genes in these cells were compared with those in the parent Y1. The level of cholesterol side-chain cleavage cytochrome P450 mRNA in the salt-inducible kinase-overexpressing cells was markedly low compared with that in the parent, while the levels of Ad4BP/steroidogenic factor-1-, ACTH receptor-, and steroidogenic acute regulatory protein-mRNAs in the former were similar to those in the latter. The ACTH-dependent expression of cholesterol side-chain cleavage cytochrome P450- and steroidogenic acute regulatory protein-mRNAs in the salt-inducible kinase-overexpressing cells was significantly repressed. The promoter activity of the cholesterol side-chain cleavage cytochrome P450 gene was assayed by using Y1 cells transfected with a human cholesterol side-chain cleavage cytochrome P450 promoter-linked reporter gene. Addition of forskolin to the culture medium enhanced the cholesterol side-chain cleavage cytochrome P450 promoter activity, but the forskolin-dependently activated promoter activity was inhibited when the cells were transfected with a salt-inducible kinase expression vector. This inhibition did not occur when the cells were transfected with a salt-inducible kinase (K56M) vector that encoded an inactive kinase. The salt-inducible kinase's inhibitory effect was also observed when nonsteroidogenic, nonAd4BP/steroidogenic factor-1 -expressing, NIH3T3 cells were used for the promoter assays. These results suggested that salt-inducible kinase might play an important role(s) in the cAMP-dependent, but Ad4BP/steroidogenic factor-1-independent, gene expression of cholesterol side-chain cleavage cytochrome P450 in adrenocortical cells.

Adrenal Cortex Neoplasms↗
PubMed2001

Differential regulation of 3beta-hydroxysteroid dehydrogenase type II and 17alpha-hydroxylase/lyase P450 in human adrenocortical carcinoma cells by epidermal growth factor and basic fibroblast growth factor.

Epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) are pluripotent growth factors that stimulate both the proliferation and steroidogenesis of adrenocortical cells. Here we demonstrate that EGF and bFGF specifically induce mRNA of 3beta-hydroxysteroid dehydrogenase type II (3betaHSD II) and suppress that of 17alpha-hydroxylase/lyase P450 (CYP17) in human adrenocortical H295R cells. The induction of 3betaHSD II mRNA did not occur until 6 h after the growth factor treatment and was completely abolished in the presence of a protein synthesis inhibitor, cycloheximide (CHX), suggesting that the induction required de novo protein synthesis. The CYP17 mRNA suppression began at almost the same time as the induction of the 3betaHSD II mRNA. Interestingly, the CYP17 mRNA level was increased by the CHX treatment. Both the 3betaHSD II and CYP17 mRNAs were repressed by treatment with a calmodulin kinase II (CaMK II) inhibitor, KN-93, and were enhanced by a mitogen-activated protein kinase (MAPK) inhibitor, PD98059. The PD98059-mediated induction of the 3betaHSD II mRNA was completely blocked by the CHX treatment. Interestingly, treatment with EGF in the presence of both PD98059 and CHX produced a greater increase in the CYP17 mRNA than did treatment in the presence of PD98059 alone. These results suggest that CHX-sensitive factor(s) and CaMK II- and MAPK-signaling pathways may have important roles in both induction of 3betaHSD II and suppression of CYP17 by EGF or bFGF in H295R cells.

3-Hydroxysteroid Dehydrogenases↗
PubMed2000

SIK (Salt-inducible kinase): regulation of ACTH-mediated steroidogenic gene expression and nuclear/cytosol redistribution.

Possible involvement of salt-inducible kinase (SIK), a serine/threonine protein kinase first cloned from high K+-diet treated rat adrenal glands, in the regulation of steroidogenesis was investigated. Y-1 cells, when treated with ACTH, underwent a rapid change in SIK's mRNA content. It reached the maximum within a few hours and returned to the base after 8 h. In contrast, the levels of mRNAs for CYP11A and StAR protein reached the maxima after 8 h. The SIK's mRNA induction failed to occur in ACTH-, forskolin- or 8-Br-cAMP-treated Kin-7 cells, a mutant cell line of Y-1 with defective cAMP-dependent protein kinase A (PKA). Y-1 cells that overexpress SIK, when treated with ACTH, had significantly repressed levels of mRNAs for CYP11A and StAR protein. Therefore, SIK might have a negative effect on the CYP11A- and StAR protein-gene expression in the early phase of ACTH-mediated steroidogenesis. To further explore the mechanisms underlying this phenomenon, we examined intracellular distribution of the green fluorescence protein (GFP)-tagged SIK. When GFP-SIK was introduced into HeLa cells, the fluorescent signals were detected in the nucleus. In Y-1 cells GFP-SIK was detected both in the nucleus and cytosol, and the signal in the former moved to the latter after ACTH-treatment. The nuclear/cytosol re-distribution of GFP-SIK was also observed in forskolin- or 8-Br-cAMP-treated Y-1 cells, but not in Kin-7 cells. These results suggest that the intracellular re-distribution of SIK in Y-1 cells may depend on the cAMP/PKA signaling pathway and has an important regulatory role in the ACTH-mediated steroidogenic gene expression.

Adrenal Cortex↗
PubMed1999

Sclerosing stromal tumor of the ovary: radiologic findings.

Sclerosing stromal tumor is a rare ovarian neoplasm. We describe the radiologic findings of sclerosing stromal tumor in two patients. In both patients, MR and CT images showed a large mass in the left adnexal region. On dynamic contrast-enhanced images, the tumors showed early peripheral enhancement with centripetal progression.

Adult↗
PubMed1998

Designing the hydrophobic core of Thermus flavus malate dehydrogenase based on side-chain packing.

We have developed a computational method for the de novo design of hydrophobic cores of proteins and tested it experimentally. The method is composed of a pair of programs, (i) to optimize side-chain conformations using an updated rotamer library for potential hydrophobic residues, based on the backbone structure of the protein of interest, and (ii) to estimate changes in Gibbs free energies between the folded and unfolded structures of the optimized sequence. Using these programs, we have engineered several variants of Thermus flavus malate dehydrogenase. To quantitate the stability change in each variant, the circular dichroism spectra of the proteins were measured as a function of guanidine hydrochloride concentration and deltadeltaG(H2O) values of the proteins were determined by extrapolation of the experimental data. However, variants with double replacements showed different denaturation cooperativity from that of the wild type and therefore it was difficult to simply compare the theoretical and experimental stability of each variant using calculated deltadeltaG and experimental deltadeltaG(H2O) values. When the calculated deltadeltaG values were compared with those at 3.5 M guanidine hydrochloride, which was the transition midpoint obtained from the denaturation curve of the wild type, good correlation was observed.

Circular Dichroism↗
PubMed1998

Trehalose 6-phosphate production with energy coupling fermentation by yeast cells.

We tried a method for the production of trehalose 6-phosphate (T6P) with energy-coupling fermentation by baker's yeast. T6P was produced in a reaction mixture containing glucose, 5'-UMP, MgSO4, inorganic phosphate, and dried cells of baker's yeast as the enzyme preparation, T6P was isolated from the reaction mixture and identified by TLC, HPLC, GC-MS, and enzymatic methods. The reaction conditions suitable for T6P production were investigated. The formation of T6P and its precursors, glucose 6-phosphate and UDPglucose, at various pHs and concentrations of substrates was examined. Accumulation of T6P was maximum with a reaction mixture containing 1 M glucose, 20 mM 5'-UMP, 20 mM MgSO4, 400 mM sodium phosphate buffer (pH 6.2), and 100 mg/ml dried cells of baker's yeast shaken at 37 degrees C for 6 h. The yield of T6P as a percentage of glucose was 11% (mol/mol) under these reaction conditions.

Adenosine Monophosphate↗
PubMed1997

Improvement of protein secondary structure prediction using binary word encoding.

We propose a binary word encoding to improve the protein secondary structure prediction. A binary word encoding encodes a local amino acid sequence to a binary word, which consists of 0 or 1. We use an encoding function to map an amino acid to 0 or 1. Using the binary word encoding, we can statistically extract the multiresidue information, which depends on more than one residue. We combine the binary word encoding with the GOR method, its modified version, which shows better accuracy, and the neural network method. The binary word encoding improves the accuracy of GOR by 2.8%. We obtain similar improvement when we combine this with the modified GOR method and the neural network method. When we use multiple sequence alignment data, the binary word encoding similarly improves the accuracy. The accuracy of our best combined method is 68.2%. In this paper, we only show improvement of the GOR and neural network method, we cannot say that the encoding improves the other methods. But the improvement by the encoding suggests that the multiresidue interaction affects the formation of secondary structure. In addition, we find that the optimal encoding function obtained by the simulated annealing method relates to nonpolarity. This means that nonpolarity is important to the multiresidue interaction.

Amino Acid Sequence↗
PubMed1997

Design of hydrophobic core of E. coli malate dehydrogenase based on the side-chain packing.

We have developed computational programs for the de novo design of hydrophobic cores of proteins. The first program optimizes side-chain conformations using an updated rotamer library for potential hydrophobic residues, based on the backbone structure of the protein of interest. The second program selects candidates to be engineered among the sequences by estimating changes in Gibbs free energy between the folded and unfolded structure of the proteins with new sequence. Using these programs, we constructed several variants of E. coli malate dehydrogenase (eMDH) which could have increased stability at 25 degrees C, compared to the wild type enzyme. To quantitate stability change between variants and the wild type, circular dichroism spectra were measured as a function of guanidine hydrochloride concentration at 25 degrees C, pH 7.0. This analysis showed that three variants constructed in this study were stabilized more than or equal to the wild type. This demonstrated that our programs may be powerful tools to design new proteins with high stability.

Amino Acid Sequence↗
PubMed1995

Detection and geometric modeling of molecular surfaces and cavities using digital mathematical morphological operations.

We developed a digital method based on mathematical morphological operations to obtain three types of surfaces: van der Waals surface, solvent-accessible surface, and molecular surface, to extract the cavities on the surface and interior part of the molecule and to extract the ligand portions in contact with the cavities. The molecular surface, the cavities and the portions, and the heme region are visualized using solid modeling. The method enables us to obtain the volumes of the cavities and inhibitor portions and the areas of the surfaces. Solid modeling enables us to obtain cross-sections at arbitrary positions. This will have considerable utility in docking studies.

Computer Graphics↗
PubMed1995

[Clinical study on antimicrobial prophylaxis following extracorporeal shock wave lithotripsy].

One hundred and sixty one patients with upper urinary stones were examined for antimicrobial prophylaxis following extracorporeal shock wave lithotripsy (ESWL). They were divided into two groups, the low-risk group (n = 133) and high-risk group (n = 28), according to the risk factors of urinary tract infection. The patients in the low-risk group were further randomized into two groups which were orally given ofloxacin for 7 days after ESWL (Group A, n = 66), no antimicrobial (Group B, n = 67). The patients in the high-risk group were randomly subdivided into three groups which were given flomoxef intravenously for 2 or 3 days and ofloxacin for 4 or 5 days thereafter (Group C, n = 10), flomoxef only for 2 or 3 days and no drugs later (Group D, n = 10), ofloxacin for 7 days (Group E, n = 8). In all of the patients in the low-risk group, during the 7 days after ESWL, fever elevation was observed in only 1.5% of patients, and bacteriuria in 10.0% on the 7th day. There was no difference in frequency of fever elevation and bacteriuria following ESWL between Group A and Group B. These findings indicate that prophylactic antimicrobial after ESWL treatment is not necessary for low risk patients with urinary tract infections. In the high-risk group, the over-all rates of fever elevation and bacteriuria were 21.4% and 24.0% respectively. The difference of effectiveness among the prophylactic regimens of the three groups (Group C, D, E) was not shown.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Dynamics of transfer RNAs analyzed by normal mode calculation.

Normal mode calculation is applied to tRNAPhe and tRNAAsp, and their structural and vibrational aspects are analyzed. Dihedral angles along the phosphate-ribose backbone (alpha, beta, gamma, epsilon, zeta) and dihedral angles of glycosyl bonds (chi) are selected as movable parameters. The calculated displacement of each atom agrees with experimental data. In modes with frequencies higher than 130 cm-1, the motions are localized around each stem and the elbow region of the L-shape. On the other hand, collective motions such as bending or twisting of arms are seen in modes with lower frequencies. Hinge axes and bend angles are calculated without prior knowledge. Movements in modes with very low frequencies are combinations of hinge bending motions with various hinge axes and bend angles. The thermal fluctuations of dihedral angles well reflect the structural characters of transfer RNAs. There are some dihedral angles of nucleotides located around the elbow region of L-shape, which fluctuate about five to six times more than the average value. Nucleotides in the position seem to be influential in the dynamics of the entire structure. The normal mode calculation seems to provide much information for the study of conformational changes of transfer RNAs induced by aminoacyl-tRNA synthetase or codon during molecular recognition.

Motion↗
PubMed1994

Energy minimization method using automata network for sequence and side-chain conformation prediction from given backbone geometry.

Globular proteins have high packing densities as a result of residue side chains in the core achieving a tight, complementary packing. The internal packing is considered the main determinant of native protein structure. From that point of view, we present here a method of energy minimization using an automata network to predict a set of amino acid sequences and their side-chain conformations from a desired backbone geometry for de novo design of proteins. Using discrete side-chain conformations, that is, rotamers, the sequence generation problem from a given backbone geometry becomes one of combinatorial problems. We focused on the residues composing the interior core region and predicted a set of amino acid sequences and their side-chain conformations only from a given backbone geometry. The kinds of residues were restricted to six hydrophobic amino acids (Ala, Ile, Met, Leu, Phe, and Val) because the core regions are almost always composed of hydrophobic residues. The obtained sequences were well packed as was the native sequence. The method can be used for automated sequence generation in the de novo design of proteins.

Bacterial Proteins↗