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Y Mokudai

Publications and source records attributed to Y Mokudai.

6 recordsLinked to original sources
PubMed1998

[Electrophysiological specification of trabecular meshwork by dielectric dispersion method].

In an attempt to observe the dielectric behavior of the trabecular meshwork and to estimate its pumping of aqueous humor quantitatively, we measured tissue impedance of the anterior portion of 22 enucleated eyeballs from 11 rabbits non-invasively with a minute coaxial surface probe. Serial measurements of five points near the limbus revealed a significant decrease of the peak value (p < 0.05, paired t-test) on loss tangent function at a point 0.5 mm from the limbus towards the sclera. We considered that the decrease in the peak value at the point was due to broadening of the dielectric dispersion reflecting the microstructure of trabecular meshwork beneath the point. After removing the corneal epithelium, the limbal epithelium, and the conjunctiva, we also observed a decrease in the peak value at the same point, which reinforced our assumption that we can identify the trabecular meshwork electrophysiologically by means of dielectric dispersion.

Animals↗
PubMed1998

[Theoretical impedance analysis of the intact rat lens with an ellipsoidal shells model].

We measured a.c. admittances for isolated rat lenses over a wide frequency range of 100 Hz to 500 MHz. In order to evade electrode polarization at low frequencies, we examined extracted lenses by direct semi-squeezing with Pt black-coated platinum electrodes. This gave rise to a 10(6) increment in permittivity at low frequencies, and two distinct dielectric dispersions were exhibited; dispersion 1 with a characteristic frequency (fc) of 2 kHz, and dispersion 2 with an fc of 2 MHz. In terms of loss tangent function, the two dispersions clearly dominated as two peaks. By curve fitting analysis with an allocated ellipsoidal-shells model based on ultrastructural features of the lens with a lens equivalent circuit, dispersion 1 was assigned to the equatorial cortex where regularly arranged lens fibers ran parallel to the applied electric field, and dispersion 2 to the nucleus of complicated fibers, combined with the polar cortex where lens fibers ran perpendicular to the electric field. Our results suggested that both lens dispersions were beta-dispersions attributable to bio-membranes.

Animals↗
PubMed1994

[Dielectric behavior of the rabbit cornea as a measure of the healing process in injured epithelium].

To correlate changes in the passive electrical properties of the rabbit cornea with quantitative grading of corneal injuries induced by topical application of 70% ethanol, we measured ocular tissue impedances using a surface electrode over the range of 10(4)-10(8) Hz and followed their temporal changes for up to 17 days. Dielectric measurements on control eyes yielded a broad dispersion curve, which, in loss tangent terms, could be decomposed into two components: dispersion 1 on the low-frequency side and dispersion 2 on the high-frequency side. By defining the peak value of the total dispersion as Pt and those of subdispersions 1 and 2 as P1 and P2, the ratios, P1/Pt and P2/Pt, were found to serve as useful indices. Upon appearance of corneal erosion due to ethanol, P1/Pt markedly increased and returned to the control level with re-epithelialization of the cornea, and the time course of P2/Pt showed a mirror image to that of P1/Pt. Both ratios correlated well with the erosion area determined photographically. These results indicate that dielectric spectroscopy is applicable to the assessment of the extent and severity of corneal injury.

Animals↗
PubMed1993

[Dielectric measurements on the rabbit cornea using a surface electrode].

Using a concentric surface electrode, we measured in situ electrical impedance in the 10 kHz-100 MHz range for the anterior portion of eyeballs isolated from white rabbits. Replacement of fluid in the anterior chamber with an equal volume of air led to decreases in conductivity, resulting in a marked alteration of impedance behavior as expressed in a loss tangent plot. Eyeballs either with corneal erosin induced through mechanical abrasion or with endothelial injury caused by a 70% ethanol replacement in the anterior chamber were subjected to impedance measurements. Dielectric analysis based on the two-term Cole-Cole equation revealed that the observed overall dielectric dispersion could be divided into two subdispersions. Of these, the first dispersion, occurring at low frequencies was associated with the endothelial layer and the second, higher-frequency dispersion was due to the epithelial layer of the cornea.

Animals↗
PubMed1991

[The hemodynamic and metabolic changes following tourniquet release during halothane anesthesia].

We measured the hemodynamic and metabolic changes following the release of lower limb tourniquet during halothane anesthesia, and discussed the cause of reduction in the blood pressure and the effective method for prevention. Cardiac index decreased transiently following the release, and gradually increased afterward. Systemic vascular resistance index decreased continuously and progressively until 10 minutes after the release. These results indicate that the causative factors of reduction in the blood pressure are temporary decrease in cardiac output and subsequent decrease in systemic vascular resistance. In mixed venous blood, pH decreased, PCO2 increased and HCO3- remained unchanged after the release. It seems that pH reduction was chiefly caused by the increase in PO2. Thus, the preventive method for reduction in the blood pressure following the tourniquet release may be as follows; 1) intravenous fluid loading, 2) hyperventilation, 3) elevation of lower limb, 4) lightning the anesthesia, and 5) finally giving vasopressors.

Anesthesia, Inhalation↗