Biomedical subjects

M Horiguchi

Publications and source records attributed to M Horiguchi.

220 records · Page 13Linked to original sources

PubMedDate not supplied

Effect of age on short-wavelength sensitive cone electroretinogram and long- and middle-wavelength sensitive cone electroretinogram.

Using a light-emitting diode (LED) built-in contact lens electrode, we studied the effect of age on short-wavelength sensitive cone electroretinograms (S-cone ERG) and long- and middle-wavelength sensitive cone ERGs (LM-cone ERG). We recorded ERGs in 31 pseudophakic subjects to avoid the effect of yellowing in the human crystalline lens. The intensities of our stimuli were on the asymptote of the intensity-response curve. Linear regression analysis against age was carried out on the S-cone ERG b-wave, and the LM-cone ERG a-, b-, and d-waves. We found significant age-dependent reduction in the amplitude of the S-cone ERG b-wave, and the LM-cone ERG a- and d-waves, significant prolongation in the peak time of the S-cone b-wave and the LM-cone ERG b-wave, significant increase in the b/a ratio of the LM-cone ERG, but no significant age correlation between the LM-cone ERG a-wave and the amplitude of the b-wave. Our results provide evidence that age-related changes in S- and LM-cone systems begin in early adulthood in the human eye. A significant increase in the b/a ratio suggests that off-bipolar cells are more vulnerable to aging than on-bipolar cells.

Adult↗

PubMedDate not supplied

Kinetics of foveal cone photopigment in myopia without chorioretinal degeneration.

PURPOSE: To study the early changes in the outer retina of myopic eyes, we performed fundus reflection foveal cone densitometry in 45 subjects with normal visual acuity and no chorioretinal degeneration (ages: 18-47 years, refraction; +2.00-(-14.50) diopters). METHODS: After full bleaching, the density of the photopigment was measured for 7 minutes by using a test spot, 562 nm in wavelength and 1 degrees in diameter, focused on the fovea. We calculated the density difference (DD) and the time constant (TC) of photopigment regeneration. RESULTS: Although we found no correlation between the DD and the refractive error, there was a significant increase in TC as the refractive error increased (r = 0.50, P < 0.01). CONCLUSIONS: These findings indicated that the kinetics of cone pigments become abnormal preceding the loss of cone cells or chorioretinal degeneration in high myopia.

Adolescent↗

PubMedDate not supplied

Amplitude decrease of photopic ERG b-wave at higher stimulus intensities in humans.

PURPOSE: The b-wave of the human photopic electroretinogram (ERG) elicited by a short-flash increases in amplitude with increasing stimulus intensities at lower stimulus levels, but then decreases at higher stimulus intensities. The purpose of the present study was to explore this phenomenon in more detail, using short- and long-flash stimuli. METHODS: The intensity-response functions of the b-wave elicited by short- and long-flashes were compared from threshold to higher stimulus intensities in 5 normal subjects. Short- and long-flash ERGs were elicited under rod-saturating background levels using white light-emitting diodes built into a contact lens electrode. RESULTS: Whereas the amplitude of the short-flash b-wave decreased at higher intensities, the amplitude of the long-flash ERG b-wave did not decrease but plateaued. The long-flash ERG d-wave or OFF-response decreased at higher stimulus levels as did the short-flash elicited b-wave. CONCLUSIONS: Because it is widely accepted that the b-wave and the OFF-response d-wave interact to produce a single positive response, our results suggest that the decrease in the b-wave amplitude at high stimulus intensity is caused by the decrease of the d-wave at the higher stimulus intensities.

Adaptation, Ocular↗

PubMedDate not supplied

Development of hepatic microsomal mixed function oxidase system in male broilers fed a high or low protein diet.

This experiment was undertaken to determine the changes in the mixed function oxidase system (MFO) in hepatic microsomes of male broiler chicks fed a 15% crude protein (LP) or 23% crude protein (HP) diet at different ages. The cytochromes P-450 and b5 content per unit of microsomal protein increased with age, while those per unit of body weight reached a maximum at 6 weeks of age, regardless of dietary protein levels. The activity of the MFO in chicks fed the HP diet was greater than those in chicks fed the LP diet during the first 9 weeks after hatching. At 4 weeks of age, cytochromes P-450 and b5, and NADPH-cytochrome c reductase were reduced by feeding the HP diet, but not by the LP diet.

Aging↗