Marzani D, Wallman J
Department of Biology, City College of the City University of New York, NY 10031, USA.
Invest Ophthalmol Vis Sci. 1997 Aug;38(9):1726-39.
Although visual deprivation causes increased ocular elongation and myopia in both birds and mammals, changes in sclera appear to be in opposite directions. Because avian sclera has a cartilaginous layer as well as the fibrous layer found in mammals, we examined whether the scleral responses to various visual manipulations differ between the two layers.
To produce increases in ocular elongation and myopia, monocular diffusers or negative lenses were fitted to eyes. Conversely, to produce decreases in ocular elongation, diffusers were removed (restoring normal vision) or monocular positive lenses were fitted. Scleral layers were then dissected apart, and incorporation of labeled precursors into glycosaminoglycans (GAGs), DNA, and protein was assessed. Tissue coculture experiments were used to assess humoral interactions between scleral layers and with the choroid.
In the cartilaginous layers, the incorporation of label into proteoglycans and DNA was significantly higher in eyes elongating faster than normal because of wearing diffusers or negative lenses and significantly lower than normal in eyes elongating slower than normal because of removal of the diffuser or wearing positive lenses. In the fibrous layers, the reverse was the case. Coculturing cartilaginous sclera from normal eyes with fibrous sclera from myopic or recovering eyes produced the same increase or decrease in sulfate incorporation into GAGs in the cartilaginous layer as though the tissue measured was from the animal providing the conditioning tissue. Coculturing with choroid, especially from recovering eyes, also inhibited cartilaginous sclera.
The fibrous layer of the avian sclera shows changes in sulfate incorporation into GAGs during deprivation and recovery from deprivation in the same direction as does the mammalian sclera, whereas the cartilaginous layer changes in the opposite direction. The responses of the cartilaginous layer may be controlled by the fibrous layer, although they are influenced by the choroid as well.
尽管视觉剥夺会导致鸟类和哺乳动物的眼轴延长及近视增加，但巩膜的变化似乎方向相反。由于鸟类巩膜既有软骨层，也有哺乳动物中存在的纤维层，我们研究了巩膜对各种视觉操作的反应在这两层之间是否存在差异。
为了使眼轴延长和近视增加，给眼睛佩戴单眼漫射器或负透镜。相反，为了使眼轴缩短，去除漫射器（恢复正常视力）或佩戴单眼正透镜。然后将巩膜层分离，并评估标记前体掺入糖胺聚糖（GAG）、DNA和蛋白质的情况。组织共培养实验用于评估巩膜层之间以及与脉络膜之间的体液相互作用。
在软骨层中，由于佩戴漫射器或负透镜而眼轴延长速度快于正常的眼睛，蛋白聚糖和DNA中标记物的掺入显著高于正常水平；而由于去除漫射器或佩戴正透镜而眼轴延长速度慢于正常的眼睛，其标记物掺入显著低于正常水平。在纤维层中，情况则相反。将正常眼睛的软骨巩膜与近视或恢复过程中眼睛的纤维巩膜进行共培养，软骨层中GAG的硫酸盐掺入量会产生与所测量组织来自提供条件组织的动物时相同的增加或减少。与脉络膜共培养，尤其是与恢复过程中眼睛的脉络膜共培养，也会抑制软骨巩膜。
鸟类巩膜的纤维层在剥夺期间和从剥夺中恢复时，GAG中硫酸盐掺入的变化方向与哺乳动物巩膜相同，而软骨层则相反。软骨层的反应可能受纤维层控制，尽管也受到脉络膜的影响。
