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Biomedical subjects

Y Kosugi

Publications and source records attributed to Y Kosugi.

At least 19 recordsLinked to original sources
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↗
PubMed1991

Open surgery assisted by the neuronavigator, a stereotactic, articulated, sensitive arm.

A new computed tomographic-stereotactic device that translates the operating point onto preoperative computed tomographic (CT) images, the Neuronavigator, has been developed. We have applied this system to various neurosurgical procedures to examine its usefulness. The system consists of a 6-joint sensing arm and a 16-bit personal computer. It projects the location of the arm tip onto a corresponding CT slice with a cursor that guides the surgeon toward the intracranial target during open surgery. The system also projects the location of the tip onto angiograms, and when used in conjunction with echography or a transcranial Doppler (TCD) flow meter, the surgeon's ability to navigate is enhanced. Sixty-eight patients underwent operation with the Neuronavigator. The navigation system worked as the core of a multimodal three-dimensional data base that proved to be useful during surgery. The maximum detection error was 2.5 mm, which was considered sufficient for open microsurgery. It also proved useful in designing the position of a craniotomy, in targeting deep-seated mass lesions, and in tracing the tumor edge, which had been identified on a CT scan. When the angiogram was combined with the navigator, it became easy to identify key vessels within a small operating field. The system was also combined with a TCD flow meter. This combination makes it possible to translate the measuring point of the TCD directly into CT coordinates, improving the precision of location of the TCD probe. The Neuronavigator combines various diagnostic images into one database and effectively guides the surgeon during surgery.

Adolescent↗
PubMed1990

New tetrapolar circuit method using magnetic field for measurement of local impedance change in biological substances.

A new tetrapolar circuit method using a magnetic field is proposed to measure the local electric impedance change in living tissue. Based on this method, we designed an apparatus which can detect impedance changes in closely-situated two parts of living tissue, simultaneously and independently. Using this apparatus, we showed the effectiveness of the proposed method by an in vitro experiment and by an in vivo measurement of pulsatile waveforms in the forearm arteries. The detection sensitivity for a local impedance change was confirmed to be higher than that of the conventional tetrapolar method. Pulsatile impedance waveforms measured in the radial and the ulnar parts of the forearm were consistent with those estimated from the anatomical structure.

Arteries↗
PubMed1989

Phase conjugation model for information transfer in the nervous system.

In the nervous system, dispersion in propagation time sometimes brings delay distortion or phase distortion on the information transmission. Also in the memory retrieval processes in the brain, some parts of images may be retrieved more slowly than others. For smooth control of fast movements as well as for keeping exact thinking, these distortions have to be taken out. To understand the distortion cancelling mechanism, new neural network models for compensating the phase distortion are proposed. The models stand on the concept of "phase conjugate mirror" which is used in optical image processing. Simulation studies based on the model resulted in successful cancellation of the delay dispersion involved in the information transmission in the nervous system.

Computer Simulation↗
PubMed1989

[Ultrasonic tissue characterization by spectral analysis of myocardial textural pattern].

Based on the fact that ultrasonic myocardial textural patterns are more irregular in the pathological myocardium than in the normal, evaluation of the myocardial tissue character was attempted in vivo using spectral analysis. Parasternal left ventricular long-axis echocardiograms were obtained from five patients with old myocardial infarction diagnosed by history, electrocardiography and coronary angiography. These echocardiograms were transferred to an image analyzer and digitized (256 x 256 x 8). The waveforms of the gray-scale-changes from the normal myocardium showed periodicity in each 8-pixel cycle, but those from the infarcted myocardium did not. To quantify pattern changes in gray-scale values in the ultrasound beam direction, spectral analysis was performed by the maximum entropy method (MEM). There were four peaks in the MEM spectra both in the normal and infarcted myocardia, but there was a great significance in these patterns: with high, steep peaks in normal MEM spectra, and low, blunt peaks in infarcted ones. By discriminatory analysis of these four peak values, normalized by the whole spatial frequencies as multivariate, the misclassification rate was 4.8-22.7% in anteroseptal infarctions and 5.0-20.0% in posterior infarctions. Thus, spectral analysis of the myocardial textural pattern has advantages for analyzing routine echocardiograms without corrections by any absolute ultrasonic references. Furthermore, the misclassification rate is so low that we are able to characterize myocardial tissue.

Echocardiography↗
PubMed1989

[A tetrapolar circuit method using magnetic field for biological resistivity measurement].

A local impedance and its change were measured using a tetrapolar circuit combined with magnetic eddy current generator. By this method, current distribution can be restricted to a desired part, so as to eliminate errors due to uncertainty of the resistance between the electrode and the skin. The resistivity of a substance in a biological model measured by this method was nearly equal to that of the substance separated from the model. Sensitivity and localization were assessed in the other model composed of a piece of metal plate in a saline pool. The detection sensitivity was validated theoretically. The localization of the impedance pulsatile waveforms, measured at the proximal part of the forearm, was consistent with that of the arteries at this part. These results suggest that this method using eddy current should expand the application area of bio-impedance measurements.

Electric Conductivity↗
PubMed1988

An interactive multivariate analysis of FCM data.

The procedure and results of the interactive multivariate analysis of FCM data are described. Using principal-components analysis, cluster analysis, and interactive maneuvers, this procedure facilitates an effective data compression from a four-dimensional space into two-dimensional space, then allows cluster separation. The procedure is especially effective for separating clusters, which are degenerated in the usual scattergrams. Programs were mostly written in C language on MS-DOS and were tested on four-dimensional analysis of the blood cells, which resulted in a successful separation of the degenerated clusters.

Cell Separation↗
PubMed1988

Effect of interferon-beta on the cell cycle of human glioma cell line U-251 MG: flow cytometric two-dimensional (BrdU/DNA) analysis.

This paper describes the determination of the effect of IFN-beta on U-251 MG cells using the bromodeoxyuridine (BrdU/DNA) analysis technique. The cell cycle perturbation of exponentially growing cells was estimated by a newly developed two-dimensional analysis of sequential BrdU/DNA distributions measured at 4-hr intervals after IFN-beta administration. The U-251 MG cell line was sensitive to IFN-beta, and cell proliferation was inhibited by 50.0% at 48 hr. Analysis of DNA histograms indicated that IFN-beta accumulated the cells in the S-phase, from 16 to 48 hr after treatment. In the two-dimensional analysis, labeled cells treated with IFN-beta moved from the S-phase through the G2M-phase and then entered the G1-phase within 12 hr after the initial treatment, in a pattern similar to labeled cells untreated with IFN-beta. After 16 hr, labeled cells treated with IFN-beta began to accumulate in the S-phase and remained there even after 48 hr. These results imply that IFN-beta may have an effect on the G1-phase, thereby inducing S-phase accumulation of human glioma cell line U-251 MG.

Bromodeoxyuridine↗
PubMed1988

[Value of exercise echocardiography in evaluating left ventricular systolic function in mitral stenosis].

Exercise echocardiography was performed for 34 patients with mitral stenosis (MS) to evaluate left ventricular (LV) systolic function. The patients were categorized in three groups according to the work loads attained: Group I, 14 patients who attained 25 watts; Group II, 10 patients, 50 watts; and Group III, 10 patients, 75 watts. Among these groups, there were no statistical differences between the resting echocardiographic LV systolic function and their cardiac catheterization data. Resting LV end-diastolic and end-systolic dimensions (EDD and ESD) did not differ by group. During exercise, EDD and ESD decreased significantly in all groups, but ESD at the maximum exercise in Group I was greater than those of the other groups. The percent fractional shortening of the left ventricle (%FS) decreased significantly with exercise in Group I, while it increased significantly in the other groups. The mean velocity of circumferential fiber shortening (mean Vcf) increased significantly in all groups, but the extent was least in Group I. The exercise-induced changes in %FS (delta %FS) and mean Vcf (delta mean Vcf) correlated closely with exercise duration (r = 0.80, r = 0.73), but this was not the case in the mitral valve area. Postoperatively, exercise echocardiography was also performed for 14 patients with mitral stenosis; two of seven patients in Group I, four of five in Group II, and two in Group III showed significant improvement in exercise tolerance after surgery. However, the other six patients showed no change in their exercise tolerance. The former patients had positive values in delta %FS and more than 0.5 circ/sec in delta mean Vcf during pre-operative evaluations, while except one patient, those who did not improve had negative delta %FS values and less than 0.5 circ/sec in delta mean Vcf. It was concluded that the change in LV systolic function during exercise echocardiography reflects LV functional reserve in patients with MS, and provides valuable information for evaluating the severity of, indications for and benefits from surgery for MS.

Blood Pressure↗
PubMed1987

Cell cycle perturbation of cultured C6 glioma cells following short-term contact with a low dose of ACNU.

The purpose of this study was to investigate the cell cycle perturbation of cultured C6 rat glioma cells induced by 1-(4-amino-2-methyl-5-pyrimidyl)methyl-3-(2-chloroethyl)3-nitrosourea hydrochloride (ACNU) using simultaneous flow cytometric measurements of DNA and bromodeoxyuridine (BrdU) content. A new graphic computer program permitted the quantification of cell density in hexagonal subareas and allowed the fraction of BrdU-labeled cells with mid-S phase DNA content (FLS) to be defined in a narrow window. The cell kinetic parameters such as cell cycle time (Tc) and S phase time (Ts) were estimated from a manually plotted FLS curve at 18 and 6 hr, respectively. The major effect of ACNU on the cell cycle was an accumulation of the cells in the G2M phase 12 to 24 hr posttreatment when compared to G2M traverse of untreated cells. For the two-dimensional analysis, cells were labeled with BrdU and then treated with ACNU, or treated with ACNU and then labeled with BrdU. It was concluded that the cells in the S and G2M phases at the time of ACNU administration progressed to mitosis but that the G1 phase cells accumulated in the subsequent G2M phase. Two-dimensional FCM analysis using BrdU provided a useful tool in studying cell cycle perturbation.

Animals↗
PubMed1986

[Left ventricular systolic performance during exercise in patients with hypertrophic cardiomyopathy].

The clinical profiles in patients with hypertrophic cardiomyopathy who had exercise-induced deterioration in systolic performance of the left ventricle (LV) were investigated using exercise echocardiography. The materials consisted of 32 patients, which who categorized in two groups according to the extent of % shortening fraction of the LV (% SF) at the peak exercise; 21 whose % SF was increased (group I: from 40.9 +/- 7.2% at rest to 44.2 +/- 8.0% at the peak exercise) and 11 whose % SF was decreased (group II: from 40.8 +/- 7.3% to 34.8 +/- 6.9%). There were no significant differences between these two groups as to the resting echocardiographic data or the prevalence of pressure gradient in the LV outflow tract. The frequency of symptoms, such as chest pain and exertional dyspnea, was higher in the group II (73%) than in the group I (38%). The time of exercise tolerance was significantly shorter in group II than in group I (I: 9.2 +/- 1.9 min., II: 7.4 +/- 2.6 min., p less than 0.05). Five patients (45%) in group II and four (19%) in group I developed at least 2 mm ST segment depression during exercise electrocardiography. Twenty-four hour ambulatory ECG monitoring showed a high prevalence of ventricular arrhythmias in group II. Seven (78%) of nine patients in group II and five (28%) of 18 in group I had abnormal 201T1 myocardial scintigrams. Left ventricular ejection fraction was not significantly different between the two groups, but the end-diastolic pressure was higher in group II (19 +/- 6 mmHg) than in group I (15 +/- 4 mmHg). All patients who underwent coronary arteriography had no significant stenosis. Thus, there are significant differences in the clinical features between the two groups of patients who had reciprocal LV responses during exercise. These findings should be considered in the management of patients with hypertrophic cardiomyopathy.

Adult↗