正常猕猴与人视网膜血管的比较

目的比较正常猕猴与人视网膜血管的异同,为进一步利用猕猴建立动物模型来研究视网膜血管打下基础。方法取健康成年猕猴眼球6只和人角膜移植供体剩余眼杯8只的视网膜,用ADP酶法进行血管染色,对两者视网膜血管的走行、血管分级、毛细血管分层以及黄斑区血管拱环等进行比较,测量结果进行统计学检验。结果猕猴与人的视网膜铺片经ADP酶法染色后见视网膜血管自穿出视盘后的一级血管逐渐分支变细,直至五级血管即毛细血管;在视盘旁、赤道部、周边部两者血管面积百分比没有差异;视盘旁血管分为多层,赤道部有两层,且深浅层间相互交通,周边部仅见一层毛细血管且较稀疏;两者黄斑区毛细血管均较密集,有形态完整呈不规则状的血管拱环,血管面积百分比以及血管拱环的面积、周长和直径没有差异。结论猕猴与人在视网膜血管走行、分级、毛细血管分层以及黄斑区血管拱环等多方面有良好的相似性,可用作人类视网膜血管、尤其是黄斑区视网膜血管研究的良好动物模型。     

青光眼视网膜神经节细胞凋亡的研究进展

青光眼视神经损伤的最后共同通路为视网膜神经节细胞的凋亡。但确切机制尚未阐明。为此,人们进行了大量相关体内、体外实验并取得一定成果。本文从凋亡的激发因素、信号传导及基因调控加以阐述。     

Thresholds for masking responses to light in three strains of retinally degenerate mice

Mutant mice with retinal degeneration (rd/rd) were given 1-h pulses of light of varying brightness at times of the night when they would normally be active. The mutant mice showed a significantly greater inhibition of locomotor activity to light (negative masking) than wildtype controls. Lack of impairment, or even enhancement of negative masking suggests that this response may depend on sparing in retinally degenerate mice of the same receptor type that mediates clock resetting, because synchronization of the circadian system is known to be unimpaired in these mutants. With very dim light pulses, mutants did not change their activity, but wildtypes actually became more active (positive masking). Positive and negative masking appear to depend on different sensory and central processes. Accepted: 11 May 1998     

Archaeal-type rhodopsins in Chlamydomonas: model structure and intracellular localization

Phototaxis in the unicellular green alga Chlamydomonas reinhardtii is mediated by rhodopsin-type photoreceptor(s). Recent expressed sequence tag database from the Kazusa DNA Research Institute has provided the basis for unequivocal identification of two archaeal-type rhodopsins in it. Here we demonstrate that one is located near the eyespot, wherein the photoreceptor(s) has long been thought to be enriched, along with the results of bioinformatic analyses. Secondary structure prediction showed that the second putative transmembrane helices (helix B) of these rhodopsins are rich in glutamate residues, and homology modeling suggested that some additional intra- or intermolecular interactions are necessary for opsin-like folding of the N-terminal ca. 300-aa membrane spanning domains of 712 and 737-aa polypeptides. These results complement physiological and electrophysiological experiments combined with the manipulation of their expression [O.A. Sineshchekov, K.H. Jung, J.H. Spudich, Proc. Natl. Sci. USA 99 (2002) 8689; G. Nagel, D. Olig, M. Fuhrmann, S. Kateriya, A.M. Musti, E. Bamberg, P. Hegemann, Science 296 (2002) 2395].     

Insulin or bFGF and C2 ceramide increase newborn rat retinal ganglion cell survival rate

Treatment of RGCs with insulin or C2 ceramide alone increased survival rate by 30%. Adding both insulin and C2 ceramide increased survival rate by 80%. Protein phosphatase 2A (PP2A) inhibitor okadaic acid (OA) eliminated the effect of C2 ceramide, but not that of insulin. Protein kinase inhibitor K252a decreased the effect of C2 ceramide in a dose-dependent manner, but the effect of insulin was not changed. Treatment of RGCs with bFGF increased survival rate by 36%. Adding both bFGF and C2 ceramide increased survival rate by 102%. OA did not alter the effect of bFGF, whereas K252a increased survival rate in a dose-dependent manner. Inhibition of C2 ceramide by OA suggests that PP2A activation is involved in its pathway, whereas PP2A is not involved in the insulin- and bFGF-activated pathway. Elimination of the effect of C2 ceramide by K252a suggests that sphingomyelin cycle activation is mediated by a protein kinase not important in the insulin-activated pathway. Moreover, the increased effect of bFGF and dose-dependently decreased effect of C2 ceramide by K252a suggest that different protein kinases are important in bFGF- and ceramide-mediated enhancement of RGC survival rate.     

Experimental retinal reattachment

In the feline model, retinal detachment initiates a cascade of changes that include photoreceptor-cell “deconstruction,” apoptotic death of some photoreceptors, neurite outgrowth from second-and third-order neurons, remodeling of photoreceptor synaptic terminals, and Müller-cell gliosis. We have previously shown that reattachment within 24 h halts or reverses many of these presumed detrimental changes. However, in patients with retinal detachments, reattachment cannot always be performed within this 24-h window. Moreover, recovery of vision following successful reattachment surgery in the macula is often imperfect. Here, we examine the ability of relatively long-term reattachment (28 d) to stop or reverse several cellular events that occur at 3 d of detachment. In contrast to earlier studies of reattachment, which focused on the regeneration of outer segments, we focus our attention here on other cellular events such as neuronal remodeling and gliosis. Some of these changes are reversed by reattachment, but reattachment itself appears to stimulate other changes that are not associated with detachment. The implications of these events for the return of vision are unknown, but they do indicate that simply reattaching the retina does not return the retina to its pre-detachment state within 28 d.     

Long-term in vivo and in vitro AAV-2-mediated RNA interference in rat retinal ganglion cells and cultured primary neurons

Viral vector-based expression of small interfering RNAs is a promising tool for gene regulation, both in cultured cells and in animal models. In this study, we analysed the ability of adeno-associated virus-2 to function as an RNAi vector in cultured primary hippocampal neurons in vitro and in retinal ganglion cells in vivo. We demonstrate a long-lasting, highly efficient, and specific down-regulation of gene expression in vivo and in vitro by the use of bicistronic vectors. This is the first evidence of a cell type-specific long-term (more than three-month-long) RNAi in the eye. Furthermore, our results constitute the prerequisite for the use of this technique in models of neurodegeneration and neuroregeneration in vivo and in vitro.     

Misfolded rhodopsin mutants display variable aggregation properties

The largest class of rhodopsin mutations causing autosomal dominant retinitis pigmentosa (adRP) is mutations that lead to misfolding and aggregation of the receptor. The misfolding mutants have been characterized biochemically, and categorized as either partial or complete misfolding mutants. This classification is incomplete and does not provide sufficient information to fully understand the disease pathogenesis and evaluate therapeutic strategies. A Förster resonance energy transfer (FRET) method was utilized to directly assess the aggregation properties of misfolding rhodopsin mutants within the cell. Partial (P23H and P267L) and complete (G188R, H211P, and P267R) misfolding mutants were characterized to reveal variability in aggregation properties. The complete misfolding mutants all behaved similarly, forming aggregates when expressed alone, minimally interacting with the wild-type receptor when coexpressed, and were unresponsive to treatment with the pharmacological chaperone 9-cis retinal. In contrast, variability was observed between the partial misfolding mutants. In the opsin form, the P23H mutant behaved similarly as the complete misfolding mutants. In contrast, the opsin form of the P267L mutant existed as both aggregates and oligomers when expressed alone and formed mostly oligomers with the wild-type receptor when coexpressed. The partial misfolding mutants both reacted similarly to the pharmacological chaperone 9-cis retinal, displaying improved folding and oligomerization when expressed alone but aggregating with wild-type receptor when coexpressed. The observed differences in aggregation properties and effect of 9-cis retinal predict different outcomes in disease pathophysiology and suggest that retinoid-based chaperones will be ineffective or even detrimental.     

Substrate Specificity and Subcellular Localization of the Aldehyde-Alcohol Redox-coupling Reaction in Carp Cones

Our previous study suggested the presence of a novel cone-specific redox reaction that generates 11-cis-retinal from 11-cis-retinol in the carp retina. This reaction is unique in that 1) both 11-cis-retinol and all-trans-retinal were required to produce 11-cis-retinal; 2) together with 11-cis-retinal, all-trans-retinol was produced at a 1:1 ratio; and 3) the addition of enzyme cofactors such as NADP(H) was not necessary. This reaction is probably part of the reactions in a cone-specific retinoid cycle required for cone visual pigment regeneration with the use of 11-cis-retinol supplied from Müller cells. In this study, using purified carp cone membrane preparations, we first confirmed that the reaction is a redox-coupling reaction between retinals and retinols. We further examined the substrate specificity, reaction mechanism, and subcellular localization of this reaction. Oxidation was specific for 11-cis-retinol and 9-cis-retinol. In contrast, reduction showed low specificity: many aldehydes, including all-trans-, 9-cis-, 11-cis-, and 13-cis-retinals and even benzaldehyde, supported the reaction. On the basis of kinetic studies of this reaction (aldehyde-alcohol redox-coupling reaction), we found that formation of a ternary complex of a retinol, an aldehyde, and a postulated enzyme seemed to be necessary, which suggested the presence of both the retinol- and aldehyde-binding sites in this enzyme. A subcellular fractionation study showed that the activity is present almost exclusively in the cone inner segment. These results suggest the presence of an effective production mechanism of 11-cis-retinal in the cone inner segment to regenerate visual pigment.     

Seasonality of Retinal Detachment Incidence and Its Associations With Climate: An 11-Year Nationwide Population-Based Study

This study aimed to examine the seasonal variability of retinal detachment (RD) in Taiwan by using an 11-yr nationwide population database. This study also investigated the association of weather conditions, i.e., ambient temperature, relative humidity, rainfall, monthly hours of sunshine, and atmospheric pressure, with RD. Data were retrospectively collected from the Taiwan National Health Insurance Research Database. The study sample included 23 718 RD hospitalizations between January 1999 and December 2009. The incidence rate of RD/100 000 people over the 132 months was computed according to sex and age groupings of <20, 20–39, 40–59, and ≥60 yrs. Then, the association between climatic factors and the monthly RD incidence rate was examined. The ARIMA (autoregressive integrated moving average) method was also employed to test the seasonality of RD incidence rates and their association with climatic factors. The annual RD incidence rates were between 7.8 and 10.8 cases/100 000 people during the study period. A fairly similar seasonal pattern of monthly RD incidence rates was apparent for males and females and males and females combined. Rates were highest August through October, decreasing in November, and lowest in February. After adjusting for time, trend, and month, the ARIMA regression models for the male, female, and males and females combined consistently revealed the monthly RD incidence rate was significantly and positively associated with ambient temperature, but negatively associated with atmospheric pressure. The authors conclude that the monthly RD incidence rates were significantly associated with seasonality. The monthly RD incidence rates were positively associated with ambient temperature and negatively associated with atmospheric pressure. (Author correspondence: henry11111@tmu.edu.tw)