Cunea Alexander, Begum Rana, Reinisch Dieter, Jeffery Glen
Institute of Ophthalmology, University College London, UK.
Vis Neurosci. 2013 Jul;30(4):169-74. doi: 10.1017/S0952523813000321. Epub 2013 Aug 28.
Photostasis is a phenomenon where the photoreceptor outer segment (OS) length and its rhodopsin content vary depending on environmental lighting. When light is reduced for extended periods, it is argued that OS lengthen and its rhodopsin concentration rises to increase photon capture in darker environment. Increases in OS length may occur because the retinal pigment epithelium (RPE) cells reduce OS consumption in prolonged darkness. But sample sizes in assessing changes in OS length have been small, and results highly varied with no statistical analysis ever offered. Further, animals used were often albinos, which have abnormal RPE cells. Here we keep pigmented and albino mice for 21 days in darkness and compare OS length with those in a normal 12:12 light/dark environment. We measured approximately 1300 OS but found no statistically significant difference in their lengths between light and dark groups in either pigmentation phenotype, although there was a small trend in the data favoring OS extension in the dark. Given that earlier studies were undertaken on limited samples with no statistical analysis, our data pose serious questions for the notion of mammalian photostasis in terms of significant OS plasticity.
光稳态是一种现象，即光感受器外段（OS）的长度及其视紫红质含量会根据环境光照而变化。当光照长时间减少时，有人认为OS会变长，其视紫红质浓度会升高，以便在较暗的环境中增加光子捕获。OS长度增加可能是因为视网膜色素上皮（RPE）细胞在长时间黑暗中减少了对OS的消耗。但是评估OS长度变化的样本量一直很小，结果差异很大，而且从未进行过统计分析。此外，所使用的动物通常是白化病小鼠，它们的RPE细胞异常。在这里，我们将有色和白化病小鼠在黑暗中饲养21天，并将OS长度与处于正常12:12光/暗环境中的小鼠进行比较。我们测量了大约1300个OS，但发现无论是哪种色素沉着表型，明暗两组的OS长度在统计学上均无显著差异，尽管数据中有一个小趋势表明黑暗中OS有延长的倾向。鉴于早期研究是在有限样本上进行的且没有统计分析，我们的数据对哺乳动物光稳态中显著的OS可塑性这一概念提出了严重质疑。
