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Biomedical subjects

M Aida

Publications and source records attributed to M Aida.

At least 37 records · Page 2Linked to original sources
PubMed1992

Adhesion between the resin shell and composite resin.

Adhesiveness between the resin shell and composite resin was examined. As the resin shell, SR-PE-ISOCETTE, made from thermosetting crown and bridge resin, was used. The shear bond strengths between the resin shell and photocurable composite resin bonded by various methods were measured after 1-day of immersion in water at 37 degrees C. Super-bond C & B treatment to the resin shell effectively improved the adhesiveness, giving a bond strength of about 14 MPa. Clearfil new bond, Clearfil porcelain bond, Unifast and MMA/TBBO treatment gave almost the same bond strengths of about 7-9 MPa. Silane coupling agents were not effective for improving the bond strength. It was revealed that 4-META was necessary for obtaining good adhesion between SR-PE-ISOCETTE and composite resin.

Boron Compounds↗
PubMed1991

A prenylflavone, artonin E, as arachidonate 5-lipoxygenase inhibitor.

Several naturally occurring prenylflavones were tested for their inhibitory actions on arachidonate 5-lipoxygenase purified from porcine leukocytes. Of the compounds tested, artonin E (5'-hydroxymorusin) exhibited the most potent inhibition on arachidonate 5-lipoxygenase (IC50 = 0.36 microM). Arachidonate 12-lipoxygenase purified from porcine leukocytes and human platelets, 15-lipoxygenase from rabbit reticulocytes and fatty acid cyclooxygenase from bovine vesicular glands were inhibited by the compound only at higher concentrations (IC50 = 2.3, 11, 5.2 and 2.5 microM, respectively).

Animals↗
PubMed1991

Molecular dynamics simulation in vacuo and in solution of cyclolinopeptide A: a conformational study.

The conformation of cyclolinopeptide A [c-(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val)], a naturally occurring peptide with remarkable cytoprotective activity, has been investigated by means of molecular dynamics simulations in various molecular environments. Structural and dynamical properties have been analyzed and compared with those experimentally determined. A detailed analysis of hydrogen bonds is reported.

Amino Acid Sequence↗
PubMed1991

[The distribution of solutions in the epidural space].

In 21 patients the distribution within the epidural space of epidurally injected 99mTc-DTPA was assessed. The gamma emissions from the epidural space were measured externally with the patients in supine position by use of a gamma camera. The recordings over the patient's back were stored in digital computer for 60 min. The results were as follows; 1) The spread of the radionuclide was mainly to cephalad direction, and seldom crossed the L5 level to sacral region. 2) The solution injected in the epidural space would distribute to less resistant compartments and the spread depends on the power of injection, negative pressure in the high epidural space and capillary pressure. 3) The elimination half-life of the injected radionuclide was between 1 to 17 min depending on the region in the epidural space. 4) The solution injected in the epidural space may penetrate dura mater at the ink cuff area and local anesthetic agents may affect the spinal nerve roots in the subarachnoid space rather than at the extra-dural space. 5) With continuous infusion technique the diffusion and penetration of the local agent through the dura mater are facilitated and more profound anesthetic effects would be expected. In clinical practice the utilization of the continuous infusion method should be considered along with the bolus injection.

Adult↗
PubMed1990

[The evaluation of commercially available silane coupling agents for porcelain adhesion].

We investigated the effectiveness of commercially available silane coupling agents on the adhesion between the composite resin and the porcelain. As silane coupling agents, we used Cosmotech primer. Clearfil porcelain bond. Porcelain liner M, and Scotchprime. As porcelain, we used Cosmotech porcelain DA2 which was etched either with hydrofluoric acid or with phosphoric acid gel. The tensile bond strengths between composite resin and the porcelain treated with silane coupling agents were measured after one day immersion in 37 degrees C water. Among the silane coupling agents, Clearfil porcelain bond gave the highest bond strength of about 175 kgf/cm2. When any of these silane coupling agents were used, the bond strengths were increased more by hydrofluoric acid etching than by phosphoric acid etching. Especially in the case of Scotchprime treatment, hydrofluoric acid etching was remarkably effective on the increase in the bond strengths. The value in hydrofluoric acid etching was 3 times higher than that in phosphoric acid etching. From SEM observation, hydrofluoric acid etching gave greater roughness to the porcelain surface, which resulted in greater mechanical interlocking of the resin. In the case of Cosmotech primer treatment, the combination with GC bonding agent did not increase the bond strengths, while combination with Clearfil new bond did. The phosphoric acid ester monomer in Clearfil new bond, which is known as strong acid, was supposed to catalyze the activation of silane coupling agent.

Adhesives↗
PubMed1989

Micronucleus induction in mouse bone marrow by phenacetin administered intraperitoneally or orally.

The extent and time course of induction of micronucleated polychromatic erythrocytes (MNPCEs) in mouse bone marrow were examined after administration of phenacetin as an insoluble suspension in olive oil by intraperitoneal injection (i.p.) or gastric intubation (p.o.) to 2 strains of mice, MS/Ae and CD-1, at doses up to 1200 mg/kg. The toxicity of phenacetin and the sensitivity of micronucleus induction differed in the 2 strains, but there was little difference in the extent of MNPCEs induced by the 2 administration routes.

Animals↗
PubMed1988

Ab initio molecular orbital study of the mispairing ability of a nucleotide base analogue, N4-aminocytosine.

The intrinsic properties of N4-aminocytosine, a base analogue of cytosine, are analyzed by an ab initio molecular orbital method. Relative stabilities of four possible isomeric structures of N4-aminocytosine are shown. The more stable isomer has the smaller dipole moment, so the relative stabilities of the isomers in solutions are subject to solvent polarity. The mutagenicity of this base analogue must arise because it can behave like either cytosine or thymine. It can form a guanine-cytosine-like base pair more easily than cytosine, and an adenine-thymine-like base pair less easily than thymine.

Chemical Phenomena↗
PubMed1988

An ab initio molecular orbital study on the sequence-dependency of DNA conformation: an evaluation of intra- and inter-strand stacking interaction energy.

The various nearest neighbor stacking interaction energies of stacked base pairs in the DNA double helix are calculated for both A- and B-type conformations using an ab initio molecular orbital method. It is demonstrated that the sequence-dependent conformational preference for A- or B-type results from the stacking interaction. In particular, the base sequence showing the highest preference for an A-type conformation is revealed as GC/GC, and the one with the next highest preference, AT/AT; for a B-type conformation, the respective sequences are CG/CG and CA/TG. The overall conformation of a DNA fragment is not determined by these particular sequences only but is influenced by all base pair steps. An intrinsically favorable conformation is predicted from the constituent stacking interaction.

Base Composition↗
PubMed1988

Intermolecular nuclear Overhauser effect and atomic pair potential approaches to wheat germ agglutinin-sugar binding.

The detailed binding mechanism of wheat germ agglutinin (WGA) with N-acetylglucosamine (GlcNAc) was investigated using intermolecular 1H-1H nuclear Overhauser effect (NOE) and atomic pair potential (APP) calculations. Negative NOE was observed on the 1H spectrum of 1-O-methyl derivative of GlcNAc in a solution containing WGA, when the aromatic region of the WGA spectrum was irradiated. Analyses of the time dependence of NOE revealed that H2 and the N-acetyl methyl protons of the sugar are in close proximity to the aromatic protons of WGA in the bound state. This was confirmed and further elucidated by the APP calculations. According to the calculation, the major binding force comes from a hydrogen-bonding between C3-OH of sugar and an acidic residue present in each of the two binding sites of WGA: Glu115 in site 1 and Asp29 in site 2. The binding is further assisted by the N-acetyl group which interacts with a few more polar amino acid residues in the binding sites. The optimized binding mode suggested by the APP calculations supports the NMR results in that H2 and a part of the N-acetyl methyl protons are within 4.5 A distance from protons of both Tyr64 and Tyr73 in site 1 and of Tyr159 in site 2.

Acetylglucosamine↗
PubMed1988

The effects of acute and chronic growth hormone (GH) administration on GH secretion in patients with idiopathic GH deficiency.

The effect of acute and chronic administration of GH on plasma GH responses to GHRH were studied in patients with idiopathic GH deficiency (GHD). Nine untreated GHD patients, 1 untreated patient with postoperative craniopharyngioma, and 7 normal short children were given synthetic human GHRH-44 (100 micrograms, iv) injection before and 2 days after being given a single dose of 4 IU biosynthetic methionyl human GH (mGH), im. Twelve GHD patients, who had been treated with 0.31-0.48 IU/kg.week pituitary-derived hGH (pdGH), im, for 8-79 months, were given GHRH 2 and 14 days after a final injection of 4 IU pdGH. Three other GHD patients were given GHRH before and after 2 yr of pdGH therapy (0.35-0.39 IU/kg.week). The GHRH-induced GH response (max delta GH) was significantly inhibited after mGH administration in the 9 untreated GHD patients [2.7 +/- 0.3 (+/- SE) vs. 4.7 +/- 0.6 micrograms/L; P less than 0.01]. The patient with secondary GH deficiency also had a marked reduction in her peak plasma GH value after mGH administration (from 32.0 to 11.7 micrograms/L). Similarly, the mean max delta GH response in the 7 normal short children was significantly inhibited by prior mGH injection (max delta GH, 12.7 +/- 2.0 vs. 28.8 +/- 4.8 micrograms/L; P less than 0.01). In the 12 treated GHD patients the GHRH-induced GH response on the 2nd day after discontinuation of pdGH therapy was significantly lower than that on the 14th day (max delta GH, 3.4 +/- 1.2 vs. 6.9 +/- 1.6 micrograms/L; P less than 0.02). In the 3 GHD patients who were studied before and after 2 yrs of pdGH therapy, the plasma GH responses were similar. In each group, plasma somatomedin-C levels on the second day after GH administration were slightly but not significantly higher than those before or 14 days after the administration. The GH responses to GHRH given on 2 occasions at 7- to 14-day intervals in individuals not receiving GH were similar in both 9 normal children and 10 GHD patients. These results indicate that acute GH administration inhibits somatotroph function in GHD patients, but chronic GH therapy does not cause irreversible damage to the somatotrophs. The acute inhibition of GHRH-induced GH release after GH administration is more likely due to direct and indirect pituitary inhibition by somatomedin-C and/or somatostatin than decreased GHRH secretion.

Adolescent↗
PubMed1987

An ab initio molecular orbital study on the characteristics of 8-hydroxyguanine.

To investigate the mechanism by which the 8-hydroxyguanine residue in DNA affects the fidelity of DNA replication, the intrinsic properties of this modified base were investigated using an ab initio molecular orbital method. The most stable 8-hydroxyguanine form was revealed to be 6,8-diketo. The addition of an oxygen atom to the 8 position of a guanine base was shown to change the electrostatic potential of the molecule entirely and to give it a negative character. This effect may influence the local structure of 8-hydroxyguanine-containing DNA and the interaction with DNA polymerase, thereby resulting in infidelity of DNA replication.

Base Composition↗
PubMed1986

An explanation of the induction of mutations by 2-aminopurine from an ab initio molecular orbital study.

The molecular mechanism of induction of mutations by 2-aminopurine (AP) was studied by an ab initio molecular orbital method. Cytosine (C) is converted to its disfavored imino tautomer more easily than AP, judging from the calculated total energies of the bases and the base analogue. This suggests that a stable AP:C base mispair via two hydrogen bonds can be formed with the imino tautomer of C. These results stress the importance of the imino form of C in AP-induced mutagenesis and support the 'trigger mechanism', in which formation of one hydrogen bond between AP and C is considered to stimulate the tautomeric shift of AP or C. The calculated relative stabilities of various base pairs and mispairs were in good agreement with experimental findings.

2-Aminopurine↗
PubMed1984

Ab initio molecular orbital study of the interaction of Li+, Na+ and K+ with the pore components of ion channels: consideration of the size, structure and selectivity of the pore of the channels.

Ab initio molecular orbital calculations were made for the various types of structures of the pore of the ion channel and the results were applied to the permeability model by Hille, an extension of the Eyring rate theory. In Hille's model, ion passage through the channel is regarded as a kinetic process. Accordingly, it is thought that the interaction energy between cation and ligand, the easier the passage is, due to the lower activation energy. The calculated interaction energy was in the order Li+ greater than Na+ greater than K+ for all models. The optimum size of the pore determined from the interaction energy depends on the structure of the filter. The size for the pentagon was largest, followed by the hexagon and tetragon. On the other hand, the size depends hardly at all on the kind of ligand molecules. In the case of the tetragon, the sizes for the Na and K channels were nearly the same as those estimated from the model building and inhibitor-blocking experiment. The interaction energy between the ionized carboxyl group and the cation was extremely large, clearly reflecting the experimental fact that the carboxyl group in the pore has an important role in making the passage of the cation through the channel easier by dehydrating the water molecules. By analysis of the interaction energy, it was revealed that the contribution of the electrostatic energy was predominant, although the contributions of the other effects might not be negligible. Among these effects, the value of the charge transfer energy is largest, and this is noteworthy in connection with the selective transmission of cations through the overlap of orbitals. It is concluded that the quantum-chemical indices such as interaction energy and the electronic charge calculated by the sophisticated ab initio method help to shed light on the nature of the pore of the ion channel.

Biological Transport↗
PubMed1983

An electron spin resonance study on the free radicals produced from aclacinomycin a and its derivatives: analysis of hyperfine structure of the spectra by means of molecular orbital method.

Quinone-containing carcinostatics, aclacinomycin A and its derivatives were investigated on the convertibility to free radical under a mild reducing condition. The hyperfine structures of electron spin resonance (ESR) spectra were satisfactorily reproduced by computer simulations, using the hyperfine coupling constants calculated by the Intermediate Neglect of Differential Overlap Molecular Orbital (INDO MO) method. This verifies the reliability of molecular orbital calculations and opens a way to analyze theoretically the correlation between chemical structures and carcinostatic activities. By analyzing hyperfine structures of ESR spectra, the free radical produced from aclacinomycin was identified as a neutral form of semiquinone radical of intact aclacinomycin. Taking into account the previous finding that 7-deoxyaklavinone (C1) is formed reductively by cytochrome P-450 reductase (EC 1.6.2.4; Komiyama et al., 1979), it is postulated that two types of semi-quinone radicals exist in vivo.

Aclarubicin↗