Lipid peroxidation and electric activity of the retina.

The induction of lipid peroxidation (LPO) by the Fe²⁺ + ascorbate system in the frog retina decreases the magnitude of the electroretinographic waves and eliminates intracellular rod light responses. The addition of antioxidants (α-tocopherol, BHT) exerts a powerful protective effect against electroretinogram suppression and simultaneous inhibition of LPO. Preincubation of the retina in a medium with α-tocopherol allows us to record intracellular rod light responses for 20–25 min, irrespective of the presence of LPO inducers. Under the effect of LPO products the photoreceptor cell membrane potentials remain unchanged despite the elimination of the light response, whereas the values of the dark membrane potential in the inner nuclear layer cells are higher than in the controls.     

Proteoglycans and collagen fibre organization in human corneoscleral tissue.

Many investigators have suggested that the acidic glycosaminoglycan component of proteoglycans may control the size and organization of collagen fibres. It was decided that the transition zone between central cornea and sclera is an ideal model for the study of the relationships between specific proteoglycans and the organization of collagen fibres. The number and size of collage fibres were correlated with the concentration and composition of acidic glycosaminoglycans at discrete intervals from mid-cornea to sclera. The concentration of acidic glycosaminoglycans is highest in the central cornea; keratan sulfate accounts for most of the acidic glycosaminoglycan and the remainder is chondroitin. The peripheral cornea has 24% less acidic glycosaminoglycan than central cornea. The proportion of keratan sulfate is decreased and chondroitin is replaced by chondroitin sulfate. Uniformity of fibre diameters and their arrangement decreases distally from the central cornea. The sharpest area of transition lies between the corneolimbus and the sclerolimbus where the rapid increase in fibre size and decrease in organization is accompanied by a rapid decrease in the concentration of acidic glycosaminoglycans (primarily a loss of keratan sulfate), and the presence of detectable quantities of dermatan sulfate. A direct relationship between degree of fibre organization and acidic glycosaminoglycan content was found. We conclude that the precisely ordered spacing of collagen fibres in the cornea is determined by specific molecular constraints imposed by the conformation of keratan sulfate proteoglycan. This study proviess further evidence that the organization of collagen fibres is controlled by proteoglycans.     

H.L.A. antigens in proliferative diabetic retinopathy

One hundred and four patients with diabetes mellitus present for at least 15 years were tissue typed for HLA antigens AI and B8. Fifty six patients had severe proliferative retinopathy and 48 patients no retinopathy. The results were compared with a group of 200 normal blood donors. There was no significant difference in frequency of AI and B8 between the two groups of diabetic patients. The HLA pattern A_I ^- B₈ ⁺ was more frequently present among the group of patients with proliferative retinopathy.     

Quality of retinal image stabilization during small natural and artificial body rotations in man

Two-dimensional head rotations recorded from 2 subjects sitting still, without artificial head support, showed appreciable movement over the frequency range d.c. to 7 Hz. Capacity of vestibuloocular reflex and visually guided eye movements to null motion over this dynamic range was examined by simultaneously recording 2-dimensional head and eye rotations while sinusoidally rotating subjects over the frequency range 0.1 to 15 Hz using small amplitudes. At best, oculomotor compensation removed about 90% of head motion from eye motion in space. Representative compensation was poorer. Compensation for natural motions of unsupported heads while sitting and standing was also incomplete resulting in substantially more eye motion in space than was observed with head supported.These observations, coupled with recent demonstrations of plasticity of the vestibulo-ocular reflex, led us to suggest that the degree of compensatory oculomotor response is actively adjusted downwards so as to guarantee sufficient retinal image motion to prevent perceptual fading when the body is relatively stationary and is actively adjusted upwards, so as to guarantee sufficient retinal stability to prevent perceptual blurring when the body moves actively. Seen this way. the goal of oculomotor compensation is not retinal image stabilization, but rather controlled retinal image motion adjusted so as to be optimal for visual processing over the full range of natural motions of the body.     

On the calcium concentration of cataractous and normal human lenses and protein fractions of cataractous lenses

Calcium concentrations of a large number of cataractous human lenses and nine normal human lenses were measured by atomic absorption spectroscopy. The mean concentration of calcium in cataractous lenses is 2–13 times higher than the mean calcium concentration of the normal lenses. In considering individual lenses, however, a large number of cataractous lenses contain either less or equivalent calcium concentrations than are present in normal lenses.The Calcium distributions in both the water-soluble and water-insoluble protein fractions isolated from yellow and brown cataracts were also determined. While some aggregate fractions of yellow lenses are calcium rich, no clearcut differences in the mean calcium concentrations of the remaining protein fractions could be established.     

Stimulus luminance and dichoptic pattern masking

The effect of stimulus luminance on dichoptic pattern masking was tested using a backward masking paradigm. Nine subjects were selected from a group of 24 (potential subjects) such that each yielded approximately equal masking results with the target stimulus in either eye. Changes in target and mask luminance produced results similar to changing interstimulus interval—the greater the luminance of the stimulus, the sooner its effect occurred. Since other studies of dichoptic pattern masking have found no effect of stimulus luminance, it is suggested that only subjects who show approximately equal masking effect with the target in either eye be included in future studies.     

消炎痛对电光性眼炎防治作用的病理学研究

本文用环加氧酶抑制剂－０．５％消炎痛油剂分别在紫外线照射前、后１５分钟滴眼，３小时后进行兔角膜组织病理学检查。对照组光镜下可见角膜上皮细胞肿胀、核碎裂、基底细胞胞浆嗜酸性染色增强；透射电镜下角膜基底层上可见坏死脱落的上皮细胞，基底细胞胞浆空泡增多，线粒体肿胀，内质网扩张。而用药组光镜下和透射电镜下见细胞结构基本正常。实验结果提示，０．５％消炎痛油剂在电光性眼炎防治方面有应用价值。     

Spectral studies on normal and cataractous intact human lenses

Spectral characteristics are presented for intact normal and cataractous human lenses. By comparison with healthy intact lenses, no new spectral features (and therefore pigmentous species) are observed in brunescent cataract. However, in this cataract, a buildup in the components giving rise to high wavelength absorption (400–500 nm) is observed relative to that at lower wavelengths (～ 300 nm). A model of protein tryptophan depletion via oxidation, resulting in protein pigmentation is considered, based on spectral evidence.