Sandberg M A, Pawlyk B S, Dan J, Arnaud B, Dryja T P, Berson E L
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Boston, Mass., USA.
Arch Ophthalmol. 1998 Jul;116(7):867-72. doi: 10.1001/archopht.116.7.867.
Recently, a mutation (Gly38Asp) was identified in the alpha subunit of rod transducin in members of the Nougaret pedigree affected with dominantly inherited stationary night blindness.
To evaluate retinal function in patients with the Gly38Asp gene defect.
Ocular examinations, including specialized measures of rod and cone function.
A clinical research facility in Boston, Mass.
A father (aged 48 years) and son (aged 25 years) with the Gly38Asp mutation.
Psychophysical thresholds to white and narrowband lights and full-field electroretinographic (ERG) responses.
Both patients showed dark-adapted thresholds to white light that were elevated approximately 2 log-units across the retina. Spectral sensitivity testing revealed thresholds that seemed to be governed mostly by rods. Although both patients' dark-adapted ERG responses to a dim blue flash were nondetectable, their dark-adapted ERGs to a white flash showed an a-wave with cone and rod components and a b-wave amplitude larger than what could have been generated by cone function alone. Rod ERGs to bright blue flashes had subnormal, but detectable, amplitudes that seemed to result from a profound reduction in sensitivity. The patients also showed loss of a cone subcomponent in the dark-adapted response to a red flash. The abnormal dark-adapted ERG responses of the patients could be simulated in the ERG responses of normal subjects tested with blue, white, and red flashes presented in the presence of a mesopic background.
Although the Nougaret form of stationary night blindness has been cited as a prototype of absent rod function with normal cone function, our findings, based on the genealogically and genotypically documented descendants of Jean Nougaret, show that rod function is present, although subnormal, and that there is slight impairment of cone function. The data also suggest that these abnormalities can be simulated by light-adapting the normal retina, compatible with the proposal that the rod transducin encoded by the mutant gene is constitutively active and that the night blindness results from partial desensitization of rods caused by the constitutive activity.
最近，在患有显性遗传性静止性夜盲的努加雷家族成员的视杆转导蛋白α亚基中发现了一种突变（Gly38Asp）。
评估Gly38Asp基因缺陷患者的视网膜功能。
眼科检查，包括视杆和视锥功能的专门检测。
马萨诸塞州波士顿的一个临床研究机构。
一名患有Gly38Asp突变的父亲（48岁）和儿子（25岁）。
对白光和窄带光的心理物理学阈值以及全视野视网膜电图（ERG）反应。
两名患者对白光的暗适应阈值在整个视网膜上均升高了约2个对数单位。光谱敏感性测试显示阈值似乎主要由视杆决定。尽管两名患者对昏暗蓝色闪光的暗适应ERG反应均无法检测到，但他们对白色闪光的暗适应ERG显示出具有视锥和视杆成分的a波以及比仅由视锥功能产生的b波振幅更大的b波。对明亮蓝色闪光的视杆ERG具有低于正常但可检测到的振幅，这似乎是由于敏感性的大幅降低所致。患者在对红色闪光的暗适应反应中还表现出视锥亚成分的丧失。在存在中间视觉背景的情况下，用蓝色、白色和红色闪光测试正常受试者的ERG反应，可以模拟患者异常的暗适应ERG反应。
尽管努加雷型静止性夜盲被认为是视杆功能缺失而视锥功能正常的典型例子，但我们基于让·努加雷有系谱和基因型记录的后代的研究结果表明，视杆功能虽然低于正常，但仍然存在，并且视锥功能有轻微受损。数据还表明，通过对正常视网膜进行光适应可以模拟这些异常，这与突变基因编码的视杆转导蛋白组成性激活以及夜盲是由组成性活性导致的视杆部分脱敏引起的提议相一致。
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