The stability of human acidic beta-crystallin oligomers and hetero-oligomers

Crystallins are bulk structural proteins of the eye lens that have to last a life time. They gradually become modified with age, denature and form light scattering centres. High thermodynamic and kinetic stability of the crystallins enables them to resist unfolding and delay cataract. Here we have made recombinant human betaA1-, betaA3-, and betaA4-crystallins. The betaA3-crystallin formed higher oligomers that lead to precipitation at ambient temperature. Heat-induced precipitation of betaA3-crystallin was compared with human and calf betaB2-crystallins, showing that the human proteins start to precipitate above 50 degrees C while the calf betaB2-crystallin stays in solution even when unfolded. The stabilities of these human acidic beta-crystallin homo-oligomers have been estimated by measuring their unfolding in urea at neutral pH. BetaA3/1/betaB1 and betaA4/betaB1-crystallin hetero-oligomers have been prepared from homo-oligomers by subunit exchange. The resolution of the methodology used was insufficient to detect a stabilization of the betaA4-crystallin subunit in the hetero-oligomer, the betaA1-crystallin subunit was clearly stabilized by its interaction with betaB1-crystallin. Circular dichroism and fluorescence spectroscopies show that homo-dimer surface tryptophans become buried in the betaA3/1/betaB1-crystallin hetero-dimer concomitant with changes in polypeptide chain conformation.     

Age-Related Changes in Cochlear Endolymphatic Potassium and Potential in CD-1 and CBA/CaJ Mice

The CD-1 mouse strain is known to have early onset of hearing loss that is progressive with aging. We sought to determine whether a disturbance of K⁺ homeostasis and pathological changes in the cochlear lateral wall were involved in the age-related hearing loss (AHL) of CD-1 as compared to the CBA/CaJ strain which has minimal AHL. In the present study, the endocochlear potential (EP) and endolymphatic K⁺ concentration ([K⁺]_e) were measured in both strains of mice with double-barrel microelectrodes at young (1–2 mo) and old (5–9 mo) ages. CBA/CaJ mice displayed no changes with aging in EP and [K⁺]_e of the basal turn. In the apical turn, there was a small positive shift of the EP (10 mV) with aging under both normoxic and acute anoxic conditions (–EP), without any change of [K⁺]_e. Further, there were no obvious pathological changes in the lateral wall of CBA/CaJ mice. By contrast, old CD-1 mice displayed a significantly reduced [K⁺]_e by 30% in both basal and apical turns with no significant changes in normoxic EP. The –EP in the apical turn was significantly reduced in magnitude by 6 mV. A severe loss of cells with aging was observed in the region of type IV fibrocytes of the apical and basal turns and of type II fibrocytes in the basal turn. A complete degeneration of organ of Corti was also observed at the basal turn of old CD-1 mice, as well as a basalward decline of spiral ganglion neuron density. The pathological changes in spiral ligament of CD-1 mice were similar to those of an inbred mouse strain C57BL/6J that expresses an AHL gene (ahl) and might be a primary etiology of AHL of CD-1 mice. These findings have ramifications for our understanding of AHL and for interpretation of genetic mutations in a CD-1 background.     

Ageing of Schlemm's canal in nonglaucomatous subjects

Aim: to study age-related Schlemm's canal endothelial changes and evaluate consequences on the filtration function. Material and methods: the inner wall endothelium of Schlemm's canal was examined in 9 non-glaucomatous subjects aged between 32 and 75 years, by a combined technique of light and electron microscopy (scanning and transmission). Quantitative analysis included counts of bulges, pores, nuclei, giant vacuoles and other protruding structures, as well as measures of pores, giant vacuoles and Schlemm's canal size parameters (diameter and inner wall width). Outflow facility calculations were realised using a modified previously described mathematical model. Results: The main structures affected by ageing in Schlemm's canal appeared to be giant vacuoles. Their density but also their size is significantly reduced with increasing age. The intracellular pore population is also found to diminish with age and is correlated to that of giant vacuoles, suggesting that those pores are luminal openings of vacuoles. Outflow facility calculations revealed a global decrease of endothelial outflow facility of about 60% between the 3rd and 7th decades. The study also showed a different age-related pattern for the two subtypes of endothelial pores. Conclusions: Our study demonstrated that Schlemm's canal filtration function is significantly influenced by age, as the endothelial inner wall outflow facility is found to be widely reduced. This is partly the result of an age-related reduction in counts of giant vacuoles and intracellular pores. The second pore population (border or intercellular) doesn't follow the same evolution, but may have a more significant regulator role in transendothelial permeability.     

正常雌猕猴骨密度与年龄关系的初步研究

目的 观察正常雌猕猴骨密度正常值范围及其与年龄的关系。方法 采用双能X线骨密度测定仪（DEXA）测量30只正常雌性猕猴骨密度,猴龄6－20岁。结果 获得正常雌猕猴峰值骨量(12－13岁）、青春期（6－8岁）和绝经初期（15－20岁）骨密度正常值,前者高于后两者,其中头骨、髋骨和全身的骨密度有显著差异。结论 正常雌猕猴增龄性骨丢失与人类相似：青春期后骨量增加,成熟期几年内达峰值,以后随增龄而减少,绝经后骨量丢失加快。     

年龄相关性黄斑变性的病因研究

年龄相关性黄斑变性(age-related macular degeneration,AMD)是发达国家老年人致盲的主要原因,在我国其发病率也呈上升趋势。它是一种由环境和遗传共同作用所导致的复杂性疾病。患病率随年龄的增加而增加。吸烟是明确的危险因素。应用基因组连锁扫描和关联分析,已经发现多个潜在的致病基因。补体因子H与AMD的关系提示替代补体途径在AMD发生发展过程中的重要作用。PLEKHA1/LOC387715/HTRA1基因位点的变异也是AMD发病的主要危险因素。理解环境和遗传因素之间的交互作用将有利于AMD预防措施和治疗手段的探索。本文对目前AMD的流行病学,发病机制和病因学的进展进行综述。     

ARMD的光学相干断层成像分析

本文给出了一种老年性黄斑变性(age-related macular degeneration,ARMD)的早期诊断方法,在ARMD的发展过程中出现的各种病理改变如玻璃膜疣、脉络膜视网膜地图状萎缩、视网膜色素上皮萎缩、脉络膜新生血管、视网膜色素上皮/神经上皮脱离等,用光学相干断层成像技术(optical coherence tomography,OCT)对其进行图像分析。     

年龄相关性白内障病因研究进展

对近年来关于年龄相关性白内障的发病机制、遗传因素和危险因素等方面新的研究进展进行综述。     

中西医结合治疗湿性年龄相关性黄斑变性的临床研究

目的探讨治疗湿性年龄相关性黄斑变性的有效方法。方法将90例(164眼)湿性年龄相关性黄斑变性的患者随机分为中药组30例54眼、西药组30例55眼及实验组30例54眼,分别予以中药、西药、中西药结合治疗。观察并比较3组疗效。结果实验组总有效率(67%)显著高于中药组(53%)及西药组(30%)(P<0.05),而中药组显著高于西药组(P<0.05)。结论中西医结合治疗湿性年龄相关性黄斑变性较其他方法为佳。     

An essential role for RPE-derived soluble VEGF in the maintenance of the choriocapillaris

Clinical and experimental observations indicate a role for VEGF secreted by the retinal pigment epithelium (RPE) in the maintenance of the choriocapillaris (CC). VEGF in mice is produced as three isoforms, VEGF120, VEGF164, and VEGF188, that differ in their ability to bind heparan sulfate proteoglycan. RPE normally produces the more soluble isoforms, VEGF120 and VEGF164, but virtually no VEGF188, reflecting the fact that molecules secreted by the RPE must diffuse across Bruch''s membrane (BrM) to reach the choriocapillaris. To determine the role of RPE-derived soluble VEGF on the choriocapillaris survival, we used mice that produce only VEGF188. VEGF188/188 mice exhibited normal choriocapillaris development. However, beginning at 7 months of age, we observed a progressive degeneration characterized by choriocapillaris atrophy, RPE and BrM abnormalities, culminating in areas of RPE loss and dramatic choroidal remodeling. Increased photoreceptor apoptosis in aged VEGF188/188 mice led to a decline in visual acuity as detected by electroretinogram (ERG). These changes are reminiscent of geographic atrophy (GA) and point to a role for RPE-derived VEGF in the maintenance of the choriocapillaris.