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Biomedical subjects

Y Kinouchi

Publications and source records attributed to Y Kinouchi.

At least 73 records · Page 4Linked to original sources
PubMed1992

Effect of intravenously infused eicosapentaenoic acid on the leukotriene generation in patients with active Crohn's disease.

Ten patients with active Crohn's disease who have been managed with parenteral-nutrition therapy were administered a lipid emulsion either with [containing 0.6 g eicosapentaenoic acid (EPA)] or without fish oil for 2 wk. We isolated polymorphonuclear leukocytes (PMNLs) from the patients before and after this treatment and measured the amounts of leukotriene B4 (LTB4) and leukotriene B5 (LTB5) generated by activated PMNLs by reversed-phase HPLC. The LTB5 generation in active Crohn's disease before this treatment was significantly lower than in healthy control subjects. The amount of LTB5 and the LTB5-LTB4 ratio increased significantly after fish-oil supplementation. The difference with LTB4 was not statistically significant. We have shown that daily intravenous administration of 0.6 g EPA influenced the generation of leukotrienes in active Crohn's disease even after short-term treatment. Further investigations are necessary to clarify the correlation between EPA and clinical improvement in Crohn's disease.

Adult↗
PubMed1992

Effects of time-varying electromagnetic fields on K+ (Rb+) fluxes and surface charge of HeLa cells.

The magnetic flux density was varied intermittently from 0.35 to 1.77T and from 0.07 to 1.54 or 1.77T by manual and automatic switchings, respectively, of the power source of an electromagnet. The durations of the "switching-on time" and "-off time" were varied but kept equal. An electric eddy current induced in the culture medium by changes in the magnetic flux density was simulated. When the durations were shorter than 10s, ouabain-sensitive Rb+ influx (active K+ influx) into cultured HeLa cells was significantly inhibited, but the ouabain-insensitive Rb+ influx (passive K+ influx) was not influenced significantly. Inhibition of active Rb+ influx increased with time during exposure for 2 h. Conversely, K+ efflux from the cells was significantly stimulated by the exposure. Microfluorometric examinations of cells loaded with the fluorescent pH indicator 4-heptadecyl-7-hydroxycoumarin (6 microM) and the membrane potential indicator diS-C3-(5) (1 microM) suggested increase in the negative charge on the cell surface during exposure. The observed changes in the K+ (Rb+) fluxes would be related to change in the electric properties of the cell surface caused by exposure to intermittent electromagnetic fields.

Cell Membrane↗
PubMed1991

Simultaneous determination of a new dihydropyridine calcium antagonist (MPC-1304) and its metabolite in dog plasma by high-performance liquid chromatography with electrochemical detection.

A rapid and sensitive high-performance liquid chromatographic analysis, with electrochemical detection, has been developed for the simultaneous determination of a new calcium-channel antagonist, (+/-)-methyl 2-oxopropyl-1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinedi carboxylate (I, MPC-1304), and its active metabolite in dog plasma. The plasma extract with toluene was chromatographed on a reversed-phase column and detected by an electrochemical detector at + 0.92 V. Calibration curves were linear from 2.0 to 100.0 ng/ml, and the detection limit was ca. 0.25 ng/ml. This method is applicable to the simultaneous determination of I and its metabolite in dog plasma following the oral administration of I.

Animals↗
PubMed1991

Artificial neural networks for source localization in the human brain.

Source localization in the brain remains an ill-posed problem unless further constraints about the type of sources and the head model are imposed. Human head is modeled in various ways depending critically on the computing power available and/or the required level of accuracy. Sophisticated and truly representative models may yield more accurate results in general, but at the cost of prohibitively long computer times and huge memory requirements. In conventional source localization techniques, solution source parameters are taken as those which minimize an index of performance, defined relative to the model-generated and clinically measured voltages. We propose the use of a neural network in the place of commonly employed minimization algorithms such as the Simplex Method and the Marquardt algorithm, which are iterative and time consuming. With the aid of the error-backpropagation technique, a neural network is trained to compute source parameters, starting from a voltage set measured on the scalp. Here we describe the methods of training the neural network and investigate its localization accuracy. Based on the results of extensive studies, we conclude that neural networks are highly feasible as source localizers. A trained neural network's independence of localization speed from the head model, and the rapid localization ability, makes it possible to employ the most complex head model with the ease of the simplest model. No initial parameters need to be guessed in order to start the calculation, implying a possible automation of the entire localization process. One may train the network on experimental data, if available, thereby possibly doing away with head models.

Brain↗
PubMed1991

Effects of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (DHPG) eye drops and cyclosporine eye drops in the treatment of herpetic stromal keratitis in rabbits.

The effect of 9-(1,3-dihydroxy-2-propoxymethyl) guanine (ganciclovir, DHPG) eye drops and the anti-inflammatory effect of cyclosporine (CYA) eye drops on experimental herpetic stromal keratitis in rabbits with herpes simplex virus (HSV) were studied. Ten rabbits were presensitized by subcutaneous injection of HSV, type 1, on days 14 and 7 before intrastromal inoculation of the same virus. These rabbits were divided into 2 groups and treatment was started 48 hours after virus inoculation. The eye drops used were 0.1% DHPG, 0.1% CYA or the vehicles of these eye drops. Eye drops were given 5 times a day and eyes were scored every day for 3 weeks after inoculation. The right eyes of Group 1 were treated with 0.1% DHPG and 0.1% CYA eye drops, and the left eyes with 0.1% DHPG and the vehicle of CYA eye drops. The right eyes of Group 2 were treated with 0.1% CYA and the vehicle of DHPG eye drops, and the left eyes with the vehicles of CYA and DHPG eye drops. The combination of DHPG and CYA was the most effective in decreasing the severity of herpetic stromal keratitis. Treatment with DHPG alone was also effective, but CYA alone was less effective.

Administration, Topical↗
PubMed1991

Development of sealed cup yoke type dental magnetic attachment.

The purpose of this study was to develop a small cup type yoke magnetic attachment sealed from oral fluid. The magnetic device forms a closed circuit between the magnet, yokes, and keeper. A 3.2 mm phi x 1.4 mm SmCO5 magnet was put into a cup yoke of 447J1 stainless steel and covered by 447J1 stainless steel disk yoke with a 316L stainless steel ring. To protect the magnet from corrosion, the connection was sealed by laser welding. The optimum dimensions were figured out by a finite element method. The performance of the magnetic attachment was investigated. As a result, a magnet device 4.4 mm in diameter and 2.1 mm in height was developed. The breakaway retention when the keeper touched it was 341 gf on average.

Dental Stress Analysis↗
PubMed1990

Measurement of the electrical bio-impedance of breast tumors.

A new impedance analytical system was developed, and measurements were performed over a frequency range of 0-200 kHz by the three-electrode method. The three electrodes consist of a coaxial needle electrode inserted into the tumor and a large reference electrode on the upper abdominal wall. The electrical bio-impedance was measured in 54 patients with breast tumors. The biological tissue can be regarded electrically as an equivalent consisting of extracellular resistance (Re), intracellular resistance (Ri), and electrical capacitance of the cell membrane (Cm). These three parameters were calculated from the measured values of electrical bio-impedance by the curve-fitting technique using a computer program. It was found that Re and Ri of breast cancers were significantly higher than those of benign tumors (p less than 0.01), and that Cm of breast cancers was significantly lower than that of benign tumors (p less than 0.01). Measurement of the electrical bio-impedance of breast tumors may have value in the differential diagnosis of breast lesions.

Adult↗
PubMed1990

Combinative improving effect of increased solubility and the use of absorption enhancers on the rectal absorption of uracil in beagle dogs.

An improvement of the rectal absorption of uracil was examined by the application of absorption enhancers in addition to the increased solubility of uracil. Uracil was ground with additives such as MgO, sodium 2,6-dihydroxybenzoate, human serum albumin or hydroxypropylmethylcellulose acetate succinate. Aqueous, oily and powdery formulations, which consisted of the ground mixtures, nicotinamide, urea and absorption enhancers such as polyoxyethylene (23) cetylether (BC-23) or sodium caprate, were prepared. Uracil solubility in the aqueous formulations was increased about 4-13 times that in the corresponding control formulations. When rectally administered to beagle dogs, marked increases in the plasma uracil level were observed in some of the cases of aqueous and oily formulations. In the powdery formulations and formulations containing macromolecular additives, however, absorption improvements was not observed. The results indicated that an improvement in the absorption of uracil was caused by the combinative improving effect of the increased uracil solubility and the promoting effect of absorption enhancers.

Absorption↗
PubMed1989

[Retention of Pt-Co magnet for dental prosthesis].

Though Pt-Co magnet is inferior to rare-earth magnet in magnetic properties, the magnet is much superior to the corrosional resistances in oral fluids. The purpose of this investigation was to determined the retentive characteristics of Pt-Co magnet. The break away force between the magnet and XM27 stainless steel keeper were measured. The retention of phi 4x 1.5 mm Pt-Co magnet was 49 g. This retention could be increased to 172 g by using stainless steel cup type yoke. These retention were rather small, but if 3 or more couples of attachments or larger Pt-Co magnet attachment were fixed in denture, the retention level approach that of clasp or mechanical precision attachments.

Cobalt↗
PubMed1989

[Sandwich type dental magnetic devices of Nd-Fe-B magnet and permendur].

Nd-Fe-B magnets have a very high maximum energy product (BH max), which is defined as the attractive strength between a magnet and opposing magnetic materials. Permendur (Fe-49 Co-2 V) has the greatest magnetic saturation (Bs), which makes it strongly magnetized. If magnetic retainers were made with Nd-Fe-B magnets and a permendur yoke, they would be small and have strong retention. The purpose of this investigation was to develop small dental magnetic devices with Nd-Fe-B magnets and permendur yokes. The magnetic devices form sandwich-type magnetic circuits with magnetic stainless steel keepers. A 4 x 3 x 2 mm rectangular prism Nd-Fe-B magnet was used. The magnet was sandwitched between the semi-columnar yokes. To protect the magnet from corrosion, the devices were encapsulated with 304 stainless steel by silver brazing and adhesion bonding of a stainless steel tube and foil. The optimum cross-sectional area of the yoke was determined experimentally. The dimensions of the devices were phi 5 x 3.5 mm for 4 x 3 x 2 magnet. The breakaway retention for a keeper of magnetic stainless steel (Type XM 27) was 852 g on average. This breakaway retention is sufficient for dental prosthetic applications.

Beryllium↗
PubMed1988

Effects of static magnetic fields on diffusion in solutions.

Static magnetic fields affect the diffusion of biological particles in solutions through the Lorentz force and Maxwell stress. These effects were analyzed theoretically to estimate the threshold field strength for these effects. Our results show that the Lorentz force suppresses the diffusion of charged particles such as Na+, K+, Ca2+, Cl-, and plasma proteins. However, the threshold is so high, i.e., more than 10(4) T, that the Lorentz force does not affect the ion diffusion at typical field strengths (a few Tesla at most). Since the threshold of gradient fields for producing a change in ion diffusion through the Maxwell stress is more than 10(5) T2/m for paramagnetic molecules (FeCl3, O2) and plasma proteins, their diffusion would be unaffected by typical gradient fields (100 T2/m at most) and even by high gradient fields (less than 10(5) T2/m) used in magnetic separation techniques. In contrast, movement of deoxygenated erythrocytes and FeCl3 colloids (more than 10(3) molecules) is influenced by the usual gradient fields due to a volume effect.

Computer Simulation↗
PubMed1988

[In vivo measurements of electrical bio-impedance of breast tumors].

The electrical bio-impedance of 17 breast tumors including 12 breast cancers and 5 fibroadenomas, were measured in vivo with three-electrode method in the frequency range of 0 to 200 KHZ. The three-electrode consists of a coaxial needle electrode inserted into the tumor and a large reference electrode on upper abdominal wall. The tissue can be regarded electrically as a equivalent consisted of extracellular resistance (R1), intracellular resistance (R2), and electric capacitance of the cell membrane (C). These three parameters were calculated from the measured values of electrical bioimpedance. It was found that R1, and R2 of breast cancers were significantly higher than those of fibroadenomas (p less than 0.001), and that C of breast cancers was significantly lower than that of fibroadenomas (p less than 0.001). The measurement of the electrical impedance of breast tumor in vivo may be useful for the differential diagnosis of breast lesions.

Adenocarcinoma, Scirrhous↗
PubMed1984

Design of a magnetic field generator for experiments on magnetic effects in cell cultures.

A magnetic field generator constructed of rare earth-cobalt magnets is proposed for examining the biological effects of static magnetic fields (less than 1 T) on tissue cultures. Important quantities of a magnetic field from a biological-effects viewpoint, ie, its strength and the product of strength and gradient, are analysed. A practical procedure for designing the generator with optimum parameters is given. Also, parameters are determined which will yield a sinusoidal spatial field distribution.

Cells, Cultured↗
PubMed1984

Sectional prostheses connected by samarium-cobalt magnets.

Large acquired defects with undercuts can be restored with sectional prostheses. Sections of the prosthesis can be connected with small Sm-Co magnet pairs. The advantages of Sm-Co magnets are that (1) sections of prostheses can be connected by magnets less than 1 cm in size, (2) they can be embedded in thin sections of acrylic resin, (3) they are easy to place, (4) insertion is easy (magnetic attraction enhances), (5) hollow obturators can be used, and (6) tissue undercuts can be used for additional retention of prostheses.

Cobalt↗