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Biomedical subjects

E Hida

Publications and source records attributed to E Hida.

10 recordsLinked to original sources
PubMed2000

Ocular surface changes after excimer laser phototherapeutic keratectomy.

PURPOSE: To study the ocular surface disorder in patients with Avellino, granular, and lattice dystrophy, band keratopathy, and corneal leukoma before and after excimer laser phototherapeutic keratectomy. DESIGN: A prospective case-controlled study. PARTICIPANTS: A total of 45 eyes of 33 patients with superficial corneal opacities seen at Kobe Kaisei Hospital, Department of Ophthalmology, and 40 eyes of 20 normal control subjects were studied. INTERVENTION: The subjects underwent routine ophthalmic examinations, corneal sensitivity measurements, tear film break up time (BUT), Schirmer test, tear film lipid layer interferometry, and conjunctival impression cytology. MAIN OUTCOME MEASURES: The patients and the control subjects were compared for prephototherapeutic keratectomy (PTK) tear function parameters, tear film lipid layer interferometry grade, goblet cell density, and conjunctival squamous metaplasia grade. Alterations of these parameters within 3 months after PTK were also looked for. RESULTS: The average pre-PTK corneal sensitivity and tear film break up time were lower in patients compared with control subjects before PTK. Tear film lipid layer interferometry grade and conjunctival squamous metaplasia grades were higher in the patients than the controls before PTK. All these parameters improved gradually and significantly after PTK. Goblet cell density was significantly lower in the patients compared with controls before PTK. Schirmer test results and goblet cell density did not show any significant alterations after PTK. CONCLUSIONS: Concurrent improvements in corneal sensitivity, tear film break up time, lipid layer interference grades, and conjunctival squamous metaplasia grades all point to the favorable effects of PTK on the ocular surface by improving the stability of the tear film and ocular surface health through attainment of a regular corneal surface and probably inducing qualitatively/quantitatively better mucin production by a healthier epithelium after PTK.

Adult↗
PubMed2000

Visual and tear function improvement after superficial phototherapeutic keratectomy (PTK) for mid-stromal corneal scarring.

PURPOSE: To study the changes in visual and tear film function following superficial excimer laser phototherapeutic keratectomy in patients with mid-stromal corneal scars. METHODS: Fourteen eyes of 14 patients with mid-stromal corneal scars seen at the Department of Ophthalmology at Kobe Kaisei Hospital underwent superficial phototherapeutic keratectomy (PTK). The subjects underwent routine ophthalmic examinations, corneal sensitivity measurements, tear film break-up time (BUT), Schrimer test and tear film lipid layer interferometry. Thirty eyes of 15 normal control subjects were also studied. The patients and the control subjects were compared for pre-PTK tear function parameters and tear film lipid layer interferometry grade. The alterations in these parameters within 6 months following PTK were also determined. RESULTS: Visual improvement was achieved in 12 eyes (86%). A hyperopic shift was observed in all eyes. The average pre-PTK corneal sensitivity and tear film BUT were lower in patients compared with control subjects before PTK. Tear film lipid layer interferometry grades were also higher in the patients than the controls before PTK. All these parameters improved gradually and significantly after PTK. Schirmer test results did not show any significant alterations after PTK. CONCLUSION: We conclude that PTK is an effective means of treating corneal scars and attaining visual improvement, even in cases with deeper corneal involvement, and may obviate the need for corneal transplantation. Simultaneous improvements in corneal sensitivity and tear film stability suggest favourable effects of PTK on the ocular surface.

Adult↗
PubMed1999

MT neurons in the macaque exhibited two types of bimodal direction tuning as predicted by a model for visual motion detection.

We previously proposed a model for detecting local image velocity on the magnocellular visual pathway (Kawakami & Okamoto (1996) Vision Research, 36, 117-147). The model detects visual motion in two stages using the hierarchical network that includes component and pattern cells in area MT. To validate the model, we predicted two types of bimodal direction tuning for MT neurons. The first type is characteristic of component cells. The tuning is bimodal when stimulated with high-speed spots, but unimodal for low-speed spots or for bars. The interval between the two peaks widens as the spot's speed increases. The second type is characteristic of pattern cells. The tuning is bimodal when stimulated with low-speed bars, but unimodal for high-speed bars or for spots. The interval widens as the bar's speed decreases. To confirm this prediction, we studied the change of direction tuning curves for moving spots and bars in area MT of macaque monkeys. Out of 35 neurons measured at various speeds, six component cells and four pattern cells revealed the predicted bimodal tunings. This result provided neurophysiological support for the validity of the model. We believe ours is the first systematic study that records the two types of bimodality in MT neurons.

Animals↗
PubMed1990

Protonation of histidine groups inhibits gating of the quisqualate/kainate channel protein in isolated catfish cone horizontal cells.

Increases in the extracellular hydrogen ion concentration ([H+]o) but not the intracellular concentration ([H+]i) antagonized the inward going membrane currents recorded from isolated cone horizontal cells during application of quisqualate, alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid, and kainate. The pK determined from a titration curve was 6.5 with a slope greater than 1, indicating protonation of several histidines. The reduction in membrane current was voltage-independent. The affinity of the agonist for the receptor, the single-channel conductance, and the open time were unaffected by [H+]o. [H+]o antagonism was not the result of charge neutralization such as screening surface charge. Diethylpyrocarbonate, a histidine-modifying reagent, reduced the agonist-induced current, but disulfide- and sulfhydryl-modifying reagents were ineffective. These results suggest that histidine groups on the external face of the channel protein provide a functional site regulating channel gating.

Animals↗
PubMed1986

Nonlinear analysis: mathematical theory and biological applications.

Wiener's method of a nonlinear system analysis and its application to neurophysiology are surveyed. His theory is explained on the orthogonal functional series expansion of a nonlinear noise with respect to the Brownian motion whose formal derivative is understood as the white Gaussian noise. Then, efforts made for applying the method to practice are discussed. Special attention is paid on relationship between the internal structure of a given nonlinear system and its kernels of the functionals. This serves to explain a meaning of the kernels. Finally, following the works of one of the authors (K-I.N.) and his colleagues, the analysis of the catfish retinal neuron system is introduced as a typical and successful example of the applications in neurophysiology.

Adaptation, Ocular↗
PubMed1984

Effects of dopamine on photopic L-type S-potentials in the catfish retina.

Photopic L-type responses were recorded from the soma and the axon terminal of horizontal cells of the catfish (Ictalurus punctatus) retina in eye-cup preparations. The responses were produced by a spot of light with 100-micron diameter (intensity, 10 microW/cm2), which was flashed or steadily illuminated and swept along a 6-mm length over the retinal surface at a speed of 0.95 mm/sec. In some experiments, a traveling random bar stimulus was used instead of the sweeping spot. While recording the responses, dopamine (DA) was applied in a jet form via a nebulizer over the retinal preparation or as superfusate to the eye-cup preparation. DA increased the response amplitude by about 50% and markedly narrowed the spatial profile of the responses from the soma but not from the axon terminal. These DA effects were observed in both normal retinas and those from which DA cells had been deprived by prior intraocular injection of 6-hydroxydopamine. Deprival of DA cells from the retina resulted in a slightly wider spatial profile of the soma and axon terminal responses than that in normal retinas. The results indicate that the spatial properties of photopic L-type responses are modulated by DA at the soma level of horizontal cells.

Animals↗
PubMed1983

A comparison of spatio-temporal receptive fields of ganglion cells in the retinas of the tadpole and adult frog.

Receptive fields formed by ganglion cells were measured simultaneously in time and space in the adult and tadpole retinas. The spatio-temporal receptive-fields (STRFs) were measured by cross-correlating the spatio-temporal white-noise stimulus with the cells' spike discharges. Crosscorrelation was made photographically to extract the first order STRF kernel (approximately linear component of the STRFs). The time-course of STRF formed by the frog ganglion cells was twice as fast as that of the tadpole cells. The STRF formed by the tadpole ganglion cells was either a center-brightening or a center-dimming type whereas in the frog there was another class of cells which produced either complex STRFs or did not show any linear component in their STRFs. Size of the STRFs in frog and tadpole was similar in both frog and tadpole retinas.

Action Potentials↗
PubMed1983

A new photographic method for mapping spatio-temporal receptive field using television snow stimulation.

A means was devised to measure simultaneously spatial as well as temporal characteristics of visual receptive fields by stimulating the retina with the noise obtained on an unused television channel. The input, television snow, and the output, neural response, were recorded on a video tape. The tape was played back to obtain the (linear) spatio-temporal Wiener kernel by cross-correlating the input with the output. This method can be applied to extract the linear part of the visual responses in time and space.

Animals↗
PubMed1982

Spatio-temporal visual receptive fields as revealed by spatio-temporal random noise.

A means was devised to visualize the retinal receptive fields in time and space using the noise on unused television channels as spatio-temporal inputs and performing correlation between the input and output photographically. The method was applied to characterize the receptive fields of catfish retinal ganglion cells. The results were 1) there were two major types of receptive fields, circular and elliptical, 2) shapes and sizes of the field components changed with time (latency), and 3) a field's surround was often localized as hot spots.

Acoustic Stimulation↗