Bettelheim F A, Churchill A C, Zigler J S
Department of Chemistry, Adelphi University, Garden City, NY 11530, USA.
Curr Eye Res. 1997 Sep;16(9):917-24. doi: 10.1076/ceyr.16.9.917.5047.
Congenital nuclear cataracts in strain 13/N guinea pigs are caused by a single splice-site mutation in the zeta-crystallin gene. Very little is known of the physical factors involved in lens opacification of this system. The aim of this study is to elucidate the biophysical processes causing the nuclear turbidity.
Normal, homozygous and heterozygous mutant guinea pig lenses were studied. Polarized light scattering measurements were performed on thin sections of lenses as a function of scattering angle. Scattering intensities were collected in two modes, I- and I+. The total water content of lenses was determined by thermogravimetric analysis. The nonfreezable (bound) water content was obtained by differential scanning calorimetry. The morphology of lenses was investigated by scanning electron microscopy.
Normal lenses scatter 5- to 10-fold less light than cataractous lenses at wide angles in both modes. The intensity ratios of the two modes imply that most of the scattering comes from density fluctuations; 10-20% of the turbidity may be contributed by orientation fluctuations. The nucleus of heterozygous cataractous lenses contain less total water than normal lenses, whereas the cortex has the same hydration as the normal lens. The nonfreezable water content of the cataractous nucleus is higher than that of the normal lens. Scanning electron microscopy showed frequent truncation of the fiber cells, cavitations and occasional longitudinal splitting resulting in hollow cylinder formation in the nucleus of the cataractous lens.
Mutation of zeta-crystallin in guinea pigs causes a congenital cataract. A number of supramolecular events contribute to the turbidity. The mobile water leaves the nuclear fiber cells, causing a collapse of supramolecular structures. Both the size of the aggregates and their refractive index increase by this dehydration process, contributing to the turbidity. The truncation and hollowing of fiber cells causes the orientation fluctuations that also increase turbidity.
13/N品系豚鼠的先天性核性白内障是由ζ-晶状体蛋白基因中的单个剪接位点突变引起的。对于该系统晶状体混浊所涉及的物理因素知之甚少。本研究的目的是阐明导致核混浊的生物物理过程。
研究了正常、纯合和杂合突变豚鼠晶状体。对晶状体薄片进行偏振光散射测量，作为散射角的函数。以两种模式收集散射强度，即I-和I+。通过热重分析测定晶状体的总含水量。通过差示扫描量热法获得不可冻（结合）水含量。通过扫描电子显微镜研究晶状体的形态。
在两种模式下，正常晶状体在广角处的散射光比白内障晶状体少5至10倍。两种模式的强度比表明，大部分散射来自密度波动；10%-20%的混浊可能由取向波动引起。杂合白内障晶状体的核总含水量低于正常晶状体，而皮质的水合作用与正常晶状体相同。白内障核的不可冻水含量高于正常晶状体。扫描电子显微镜显示，纤维细胞频繁截断、出现空洞，偶尔出现纵向分裂，导致白内障晶状体核中形成空心圆柱体。
豚鼠ζ-晶状体蛋白突变导致先天性白内障。许多超分子事件导致混浊。流动水离开核纤维细胞，导致超分子结构塌陷。通过这种脱水过程，聚集体的大小及其折射率均增加，导致混浊。纤维细胞的截断和空洞化导致取向波动，也增加了混浊。
