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Biomedical subjects

E Tamiya

Publications and source records attributed to E Tamiya.

At least 19 recordsLinked to original sources
PubMed1992

Ultramicrobiosensors for monitoring of neurotransmitters.

Carbon fiber electrodes are used to construct ultramicrobiosensors with 7-15 microns diameter. Electrochemical operations for preelectrolysis and measuring were examined for sensitive determination of hydrogen peroxide. Determination limit was 0.1 microM of hydrogen peroxide. Reproducible determination of hydrogen peroxide is possible even in samples containing albumin protein. A micro-acetylcholine sensor was fabricated by immobilizing acetylcholine esterase and choline oxidase on the carbon fiber by entrapment with PVA-SbQ. This sensor gave a linear calibration plot for the range from 0.1 to 1.0 mM with a linear correlation coefficient of 0.9842. A micro-glutamate sensor consisted of a platinized carbon fiber disk electrode modified with immobilized glutamate oxidase membrane. This sensor gave a linear calibration for the range 2 microM to 1.2 mM. Release of glutamate in the cerebellar cortex was detected after potassium stimulation.

Acetylcholine↗
PubMed1992

Bioluminescence detection system of mutagen using firefly luciferase genes introduced in Escherichia coli lysogenic strain.

A rapid and convenient microbial sensing system for mutagens was developed based upon the induction of prophage from Escherichia coli lysogenic strain and bioluminescence. The system consisted of lysogenic E. coli encoding firefly luciferase genes and a photodetection system. Measurement of mutagen mitomycin C was achieved by measuring the luminescence intensity emitted from E. coli lysogenic strain for the recombinant phage in the presence of luminescence substrates. Approximately 1 h after addition of mitomycin C, the luminescence began to be observed, and 3 h after, it attained a level of 2 times greater than that of 1 h. Irradiation with ultraviolet light also produced light based on induction of phage from the E. coli lysogenic strain for the recombinant phage. On the other hand, when nonmutagenic toxic compounds like sodium azide were added to the reaction medium, luminescence was not observed. Mitomycin C could be detected within 1 h with this sensing system, at concentrations down to 10(2) ng/assay.

Bacteriophage lambda↗
PubMed1992

A biocompatible needle-type glucose sensor based on platinum-electroplated carbon electrode.

A biocompatible needle-type glucose sensor with a 3-electrode configuration was constructed. A platinum-electroplated carbon stick was used as the working electrode, Ag/AgCl as the reference electrode, and a disposable hypodermic needle made of stainless steel as the counter electrode. A Nafion membrane, an immobilized glucose oxidase (GOD) membrane, and a biocompatible membrane with diffusion-limiting effect were coated successively onto the working electrode. The sensor showed a rapid response (< 120 s in batch operation), good reproducibility (RE < 3%), good stability (over 36 h in control serum), a wide dynamic range (5-600 mg/dL glucose), and superior biocompatibility. It was used to determine glucose in serum. The data obtained from the sensor showed good agreement with that from a clinical autoanalyzer (R > 0.95).

Biocompatible Materials↗
PubMed1992

A novel microbial sensor using luminous bacteria.

A novel microbial sensor system that uses luminous bacteria was developed for the determination of both glucose and toxic compounds. The sensor system consisted of a membrane with luminous bacteria immobilized upon it and a photomultiplier. Measurements were based on the in vivo intensity of the light emitted by the bacteria, as this is affected by their environment. A linear relationship was observed between increased luminescence and concentrations of glucose between 0.05 mM and 0.55 mM. The relative standard deviation was 10% for 0.55 mM glucose (n = 10). Toxic compounds such as benzalkonium chloride, sodium dodecyl sulphate and chromium(VI) were also detected by measuring the decrease in luminescence in their presence.

Bacteria↗
PubMed1992

Detection of coronary artery calcification by X-ray computed tomography and its significance: a new CT scoring technique.

In order to study the utility of X-ray computed tomography (CT) for the evaluation of coronary stenosis, the authors developed a scoring system for calcification seen through CT and compared the results with coronary angiographic (CAG) findings (Friesinger's scoring system). Their study included 143 patients (angina pectoris 53, myocardial infarction 44, control 46) who received both CT and CAG. Judkins method was selected for CAG, and stenosis greater than or equal to 75% was defined as significant. Horizontal slices of CT from ascending aorta to cardiac apex at 1 cm intervals were imaged without contrast enhancement. CT scoring system was as follows: no calcification = 0, the length of calcification less than 1 cm = 1, 1-2 cm = 2, more than 2 cm = 3 points. They then totaled the separate scores of all the slices for each coronary artery. Sensitivity, specificity, and predictive value of CT against coronary stenosis were good (79%, 80%, 69%, respectively). The correlation between CT and CAG scores was significant (r = 0.644, p less than 0.01). For all coronary arteries, no correlation was found between the CAG and CT findings for patients less than forty-five years of age. However, from 45 years of age upward, the results were significant. Until now, to the best of their knowledge, no satisfactory system to define the severity of coronary calcification has existed. Density cannot be used, because values are dependent on the area of the region of interest used. They demonstrated the considerable potential usefulness of CT in predicting the presence of coronary stenosis and analyzing its severity.

Calcinosis↗
PubMed1992

[Assessment of coronary artery bypass grafts by X-ray computed tomography with and without contrast enhancement].

To assess the patency of coronary artery bypass grafts, we tested the capability of X-ray computed tomography (CT) with and without contrast enhancement. This procedure was used on 63 grafts (30 in the LAD; 20 in the LCX; 13 in the RCA) in 32 patients with a mean age of 56 +/- 8 years, all of whom were referred to our department for postoperative management or evaluation. The CT scanner used was Toshiba TCT-60A with a scan time of 3 sec, 5 mm thick slices, and 512 x 512 pixels. CT scans without contrast enhancement were obtained from the level of the aortic arch to the left ventricle. Eight sec after 30 ml of contrast media was injected at a rate of 3 ml/sec into an antecubital vein, 5 scans were made at the same level of the pulmonary artery truncus. After positioning the regions of interests on the ascending aorta and grafts, we obtained time-density curves (TDCs) and compared the data with those recorded from an intraoperative electromagnetic flow meter (EMF). Fifty grafts were angiographically patent. The appearance time, build-up time, peak time, disappearance time and peak densities obtained from TDCs of grafts did not correlate with the flow volumes measured by EMF. Patent grafts were easily identified visually, without contrast enhancement (sensitivity; 88%, specificity; 100%, accuracy; 91%). Occluded grafts were not imaged on CT, either with or without contrast enhancement. We concluded that the TDCs of grafts obtained by CT are of no value for predicting the graft flow, and that plain CT without contrast enhancement is sufficiently useful for assessing the patency of such grafts.

Aged↗
PubMed1992

[Doppler and echocardiographic study of normal systolic murmurs].

To elucidate the genesis of normal ejection systolic murmurs, we performed phono and Doppler echocardiography in 42 normal subjects. Individuals with hypertension, ST.T changes on ECG, anemia or other cases with definite cardiovascular findings were excluded from the study. Their ages ranged from 22 to 61 years with an average of 48.1 years. They were classified in 2 groups; 9 with Levine 2/6 systolic murmur and 33 without murmur or with 1/6 murmur. Fifteen patients with pure aortic regurgitation or with aortic prosthesis but without significant stenosis, and 7 patients with pulmonic valvular stenosis were served as control. We correlated the intensity and timing of murmur with maximal flow velocity, acceleration time and other parameters. All systolic murmurs were early systolic. Mid-systolic murmur was not noted. Peak of flow velocity increased at the aortic orifice than at the left ventricular outflow tract or pulmonary orifice. Left-sided peak flow velocity occurred earlier than the right-sided peak flow velocity. Early systolic maximal flow velocity of the aorta significantly increased in 9 subjects with murmur than in the remaining 33 without significant murmur. Ejection fraction, hematocrit and body surface area did not differ between the groups with and without significant murmur. Systolic blood pressure and age, however, were higher in subjects with murmur. In aortic valvular disease, systolic murmurs and peak flow signals were early systolic, but in pulmonary stenosis these were mid-systolic in timing. In conclusion, normal ejection systolic murmurs were early systolic and originated at the aortic orifice. Mid-systolic murmurs were unlikely as left-sided murmur in origin. Flow velocity was the most important determinant of the intensity of ejection murmur.

Adult↗
PubMed1991

Amplification immunoassay for the determination of hepatitis B surface antigen.

A sensitive sandwich immunoassay for the determination of Hepatitis B surface antigen (HBs) was developed, using a cascade system of Limulus amebocyte lysate as a signal amplification system. Lipopolysaccharide (LPS) was conjugated to anti-HBs antibody. Anti-HBs antibody was adsorbed to polystyrene beads. First, HBs were reacted to solid phase anti-HBs antibody (a-HBs). After the reaction, the beads were rinsed, and were then reacted with a-HBs-LPS. Then, LPS activity specifically bound to the beads was measured. HBs could be measured in the range of 10(-10)-10(-12) g/mL.

Hepatitis B Antibodies↗
PubMed1991

Fluorescence polarization immunoassay employing immobilized antibody.

The use of an antibody immobilized on latex or silver colloid in fluorescence polarization immunoassay (FPI) is assessed. In FPI it is possible to detect antigens of high molecular weight because the molecular weight of the antibody is effectively increased. In the assay for rabbit immunoglobulin G a limit of detection lower by two orders of magnitude and an assay range wider by one order of magnitude can be obtained in comparison with conventional FPI. The detection limit is 10(-10) mol l-1 and the total assay time for one sample is 8 min. This assay combines a low detection limit with a short assay time.

Animals↗
PubMed1991

Development of acetylcholine sensor using carbon fiber (amperometric determination).

An enzyme sensor is developed using carbon fiber to measure acetylcholine concentration. The mechanism is based on the detection of H2O2 which is a product of the sequential enzyme reactions of acetylcholinesterase and choline oxidase. The fabrication of the electrode is described. The sensor is polarized at 1.2 V. Enzymes are co-immobilized in polyvinyl alcohol containing styryl pyrydinium (photo-crosslinkable polymer). A fast response time of 0.8 min is obtained. A linear correlation is observed between 0.2 and 1.0 mM. Other optimal operational conditions with respect to pH, temperature and stability are discussed. The use of carbon fiber containing co-immobilized enzymes could offer several novel advantages especially in neuroscience research. In conclusion, the aims of the present work are centered on carbon fiber electrode fabrication, immobilization and electrochemical measurements.

Acetylcholine↗
PubMed1991

[Prediction of coronary artery bypass graft flow--analysis of time density curve obtained from digital subtraction angiography].

UNLABELLED: To predict the coronary artery bypass graft(CABG) flow based on the time density curve(TDC) obtained from the digital subtraction aortograms(DSA), we developed a pulsatile CABG model (perfusion pressure 60, 130 mmHg, pulse rate 53, 126/min, cardiac output 3-7 l/min, diameter of the graft 2.1-6.0 mm). After positioning the regions of interest (ROI), we injected contrast medium (5-40 ml/sec, 5-40 ml) into the outlet conduit. Concerning the TDCs, we calculated appearance time(Ta), peak densities(Dp), peak time(Tp), disappearance time(Td), integral of TDC, delta Tp (difference of Tp between two ROI) and delta Ta (difference of Ta between two ROI). RESULTS: Perfusion pressure, graft flow and output curve were similar to those of patients with CABG. Ta, Tp, Td and delta Tp were affected by both the injection rate and the volume of the contrast medium; while Dp and the TDC integral were only affected by the latter parameter. Under the same conditions of contrast medium injection, the TDC depended strongly on graft flow, diameter of the graft, output and pulse rate. 21.6 + 0.92 pi.d2/4.delta 1/delta Tp.60 provided the most accurate estimation of CABG flow (r = 0.865, p less than 0.01). We conclude that densitometric analysis of DSA may be useful in the prediction of CABG flow.

Absorptiometry, Photon↗
PubMed1990

Microbiosensors.

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Biosensing Techniques↗
PubMed1989

[Detection and significance of calcified coronary arteries by computed tomography].

To investigate whether coronary artery disease is detected noninvasively, we correlated calcification on computed tomography (CT) with coronary angiographic (CAG) findings in 90 consecutive patients including 48 with angina pectoris or myocardial infarction. The mean age was 52.2 years and 83% were men. CT scans without contrast enhancement (3 sec scan time) were obtained at 1 cm thickness from the ascending aorta to cardiac apex to identify calcification in coronary arteries. Results; CAG revealed of 50 patients, and stenosis was present more often at calcified vessels on CT. (table; see text) Calcification occurred more often in 2 or 3 vessel disease. However, stenotic segments were not always calcified. We conclude that CT is sensitive for the detection of calcification and an important method for the diagnosis of coronary artery disease.

Calcinosis↗
PubMed1988

DNA cleavage based on high voltage electric pulse.

A high voltage electric pulse was applied to DNA cleavage. The DNA cleavage reaction was dependent on the voltage amplitude, pulse number and pulse width. Radical scavengers and ESR data indicated the possibility that active species such as OH radical were strongly related to DNA cleavage.

DNA↗