Knighton R W, Huang X, Zhou Q
Bascom Palmer Eye Institute, University of Miami School of Medicine, Florida 33101, USA.
Invest Ophthalmol Vis Sci. 1998 Jan;39(1):189-93.
The reflectance of the retinal nerve fiber layer (RNFL) arises from cylindrical light scattering elements distributed throughout its thickness. To determine whether these elements include axonal microtubules, eyecup preparations of the toad Bufo marinus were treated with the microtubule depolymerizing agent colchicine.
Some eyecups were incubated for various times in different colchicine concentrations and then fixed and prepared for electron microscopy (EM). In other eyecups the reflectance of the RNFL at 440 nm was measured by means of imaging microreflectometry. After a period of baseline measurements, the bathing solution was changed either to one of identical composition (control experiments) or to one containing 10 mM colchicine. Measurements then continued for 2 to 3 hours.
Quantitative EM showed that colchicine caused the density of axonal microtubules to decrease by approximately one third in 2 hours. Reflectometry showed, in control experiments, that the RNFL reflectance remained near baseline for the duration of an experiment. In contrast, after changing to colchicine solution, the RNFL reflectance declined to a level 37% to 55% below baseline.
Microtubules made a major contribution to the 440-nm reflectance of the unmyelinated axons of the toad RNFL and could make a similar contribution to the reflectance of human RNFL.
视网膜神经纤维层（RNFL）的反射率源于分布于其整个厚度的圆柱形光散射元件。为了确定这些元件是否包括轴突微管，对海蟾蜍（Bufo marinus）的眼杯标本用微管解聚剂秋水仙碱进行处理。
将一些眼杯在不同浓度的秋水仙碱中孵育不同时间，然后固定并制备用于电子显微镜（EM）观察。在其他眼杯中，通过成像显微反射测量法测量RNFL在440nm处的反射率。在进行一段时间的基线测量后，将浴液换成成分相同的溶液（对照实验）或含有10mM秋水仙碱的溶液。然后继续测量2至3小时。
定量EM显示，秋水仙碱使轴突微管的密度在2小时内降低了约三分之一。反射测量显示，在对照实验中，RNFL反射率在实验期间保持在基线附近。相比之下，换成秋水仙碱溶液后，RNFL反射率下降至比基线低37%至55%的水平。
微管对蟾蜍RNFL无髓鞘轴突在440nm处的反射率有主要贡献，并且可能对人类RNFL的反射率有类似贡献。
