Electrophysiological and pathological studies on Creutzfeldt-Jakob disease with retinal involvement

In a case of Creutzfeldt-Jakob disease in a 59-year-old female, multifocal degeneration from the cerebral cortex through the visual pathway to the retina was detected clinically, electrophysiologically, and pathologically.Visual evoked cortical potentials (VECPs) showed a peculiar huge negative wave in the early stage but the amplitude reduced gradually. The a- and b-waves of the ERG were detectable in the final stage. Dynamic topography of VECPs revealed a delay of excitation in the visual cortex in the early stage, but a complete defect of the cortical potential and diminished reactivity of the brain stem were apparent in the later stage.Pathological findings were the spongy degeneration of the cerebral cortex, demyelination of the white matter and the optic pathway, and the degeneration of the nerve fiber layer and ganglion cell layer of the retina.     

正常眼多焦视网膜电图特征的初步探讨

目的 :初步分析正常人眼多焦视网膜电图 (m ERG)测量值 ,并探讨正常眼视网膜后极部不同部位的电生理功能。方法 :对 19例 (2 5眼 )散瞳正常眼作多焦视网膜电图检查 ,记录 6 1个部位反应波形图 ,分析视网膜后极部不同区域的a波 (第 1个负波 )和b波 (第 1个正波 )的潜伏期、振幅值及振幅密度。结果 :视网膜后极部中心环 (第 1环 )振幅密度为最高 ,a波为 (33.92± 18.95 )nV/deg2 ,b波为 (6 8.78±19.84 )nV/deg2 ,随着离心度的增加 ,各振幅密度逐渐下降 ,差异有显著性 (P <0 .0 1)。a波及b波潜伏期、振幅及振幅密度在四个象限的差异均无显著性 (P >0 .0 5 )。结论 :多焦视网膜电图能客观、定位、定量地测定视网膜后极部不同部位的视功能 ,其测定的正常值为临床研究提供了参考数值     

Computation of the luminance and pattern components of the bar pattern electroretinogram

Pattern onset electroretinograms (PERGs) were recorded from four normal subjects. Square-wave gratings of 75% contrast were presented in three approximately contiguous, concentric zones of outer angular radius, 5.1°, 12.6°, and 23.6°. The zones were calculated to give equal numbers of ganglion cell receptive fields. The recorded PERGs were considered to include luminance and pattern components which have low and bandpass spatial tuning functions respectively. These components combine in the PERG to produce a broad spatial tuning characteristic. The amplitude of PERGs in response to low spatial frequency stimuli is widely reported to be linearly related to contrast. The retinal illuminance response at every spatial frequency was computed from the eye's modulation transfer function. This function characterizes the reduction in contrast that occurs because of optical degradation. The computed retinal illuminance response was subtracted from the PERG waveform and a pattern-specific response was revealed. The latter had a highly tuned bandpass function which peaked at higher spatial frequencies than the PERG at corresponding peripheral angles.     

The effect of diphenylhydantoin on the electroretinogram

Acute administration of diphenylhydantoin (DPH) in rabbits produces a significant increase in the amplitude of the a-wave. A marked increase in the amplitude of the b-wave is also noted but the time course is slower than that for the a-wave. While in controls the oscillatory potential (OP) recordings essentially consist of three major types, recordings taken after DPH injection consist of one major OP (OP₂), which appears to be a result of the fusion of the original OP₂ with another OP produced by the DPH injection. A similar blend of OPs was also seen in ERGs recorded from three human subjects on DPH therapy.     

Influence of isobutylmethylxanthine on the direct current electroretinogram of albino rabbit eyes

The direct current electroretinogram and the standing potential of the eye were recorded from both eyes of unilaterally vitrectomized albino rabbits. The effect of intraocular irrigation with the nonselective phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) was compared with that of a balanced salt control solution. IBMX (0.5mM) produced a reversible increase in the amplitudes of the a-wave (19%, p < 0.02), b-wave(21%, p < 0.001) and c-wave (12%, p < 0.01) of the electroretinogram. A small elevation of the standing potential was found (0.4 ± 0.2mV), but this increase was not statistically significant (p > 0.05). The results indicate a primary and principal influence of IBMX on the photoreceptors.     

Imaging signal transduction via arachidonic acid in the human brain during visual stimulation, by means of positron emission tomography

BACKGROUND: Arachidonic acid (AA, 20:4n-6), an important second messenger, is released from membrane phospholipid following receptor mediated activation of phospholipase A(2) (PLA(2)). This signaling process can be imaged in brain as a regional brain AA incorporation coefficient K*. HYPOTHESIS: K* will be increased in brain visual areas of subjects submitted to visual stimulation. SUBJECTS AND METHODS: Regional values of K* were measured with positron emission tomography (PET), following the intravenous injection of [1-(11)C]AA, in 16 healthy volunteers subjected to visual stimulation at flash frequencies 2.9 Hz (8 subjects) or 7.8 Hz (8 subjects), compared with the dark (0 Hz) condition. Regional cerebral blood flow (rCBF) was measured with intravenous [(15)O]water under comparable conditions. RESULTS: During flash stimulation at 2.9 Hz or 7.8 Hz vs. 0 Hz, K* was increased significantly by 2.3-8.9% in Brodmann areas 17, 18 and 19, and in additional frontal, parietal and temporal cortical regions. rCBF was increased significantly by 3.1-22%, often in comparable regions. Increments at 7.8 Hz often exceeded those at 2.9 Hz for both K* and rCBF. Decrements in both parameters also were produced, particularly in frontal brain regions. CONCLUSIONS: AA plays a role in signaling processes provoked by visual stimulation, since visual stimulation at flash frequencies of 2.9 and 7.8 Hz compared to 0 Hz modifies both K* for AA and rCBF in visual and related areas of the human brain. The two-stimulus condition paradigm of this study might be used with PET to image effects of other functional activations and of drugs on brain signaling via AA.     

VEP及ERG联合检查1456例患者的临床分析

目的：分析视觉电生理检查病例，探讨该检查技术在视觉功能评定中的作用。方法：对2004年10月-2006年10月接受VEP及ERG检查的病例资料进行回顾性分析，以临床第一诊断为依据进行统计。结果：共1456例患者接受检查，年龄分布在4岁-87岁之间。疾病分类表明本组病例主要集中于白内障、眼外伤、视力下降原因待查、青光眼、视网膜脱离、视神经疾病及其他视网膜疾病等方面，占总数的91．28％。电生理检查结果主要表现为幅值降低或（和）潜伏期延迟。结论：视觉电生理学检查能够客观反映视觉功能，适用于临床诊断、术前预测、疗效评价、疾病预后、医学鉴定。但也有一定的局限性，须联合检查多项电生理指标并结合临床情况才能够作出正确结论。     

Defective ceramide synthases in mice cause reduced amplitudes in electroretinograms and altered sphingolipid composition in retina and cornea

Complex sphingolipids are strongly expressed in neuronal tissue and contain ceramides in their backbone. Ceramides are synthesized by six ceramide synthases (CerS1–6). Although it is known that each tissue has a unique profile of ceramide synthase expression and ceramide synthases are implicated in several neurodegenerative disorders, the expression of ceramide synthase isoforms has not been investigated in the retina. Here we demonstrate CerS1, CerS2 and CerS4 expression in mouse retina and cornea, with CerS4 ubiquitously expressed in all retinal neurons and Müller cells. To test whether ceramide synthase deficiency affects retinal function, we compared electroretinograms and retina morphology between wild‐type and CerS1‐, CerS2‐ and CerS4‐deficient mice. Electroretinograms were strongly reduced in amplitude in ceramide synthase‐deficient mice, suggesting that signalling in the outer retina is affected. However, the number of photoreceptors and cone outer segment length were unaltered and no changes in retinal layer thickness or synaptic structures were found. Mass spectrometric analyses of ceramides, hexosyl‐ceramides and sphingomyelins showed that C20 to C24 acyl‐containing species were decreased whereas C16‐containing species were increased in the retina of ceramide synthase‐deficient mice. Similar but smaller changes were also found in the cornea. Thus, we hypothesize that the replacement of very long‐chain fatty acyl residues by shorter C16 residues may affect the electrical properties of retina and cornea, and alter receptor‐mediated signal transduction, vesicle‐mediated synaptic transmission or corneal light transmission. Future studies need to identify the molecular targets of ceramides or derived sphingolipids in light signal transduction and transmission in the eye.     

糖尿病早期视网膜神经组织病理性改变研究进展

糖尿病视网膜病变（DR）是主要的致盲眼病。一直认为，视网膜微血管在糖尿病视网膜病理改变中发挥了主导作用。最近研究显示，在DR过程中有神经元的凋亡、神经胶质细胞功能障碍及视觉电生理等改变且先于视网膜微血管病变。本文综述近年来DR视网膜神经组织的国内外研究进展。     

局部应用医用生物蛋白胶释放NGF治疗大鼠视神经不完全损伤

目的研究局部应用医用生物蛋白胶释放神经生长因子(NGF)对大鼠视神经不完全损伤的治疗作用。方法将含有NGF生物蛋白胶放入培养基,于不同时间检测培养基中NGF的活性。将24只SD雄性大鼠随机分为假手术组(第1组),空白对照组(第2组),NGF肌注组(第3组)和实验组(第4组);每组6只。用手术造成左侧视神经不完全性损伤。第3组术后肌注NGF450U/d,共10d;第4组术中于损伤视神经局部注入生物蛋白胶0.2m(l含NGF450U),分别于术后第14、28天进行闪光视觉诱发电位(F-VEP)检测和视网膜节细胞(RGC)计数。结果 NGF在10h内逐渐从生物蛋白胶中释放至培养基。与第1组相比,第2、3、4组在术后第14天受损视神经的F-VEPP1潜伏期分别延长100%、45.5%和13.6%,波幅分别下降58.6%、44.6%和21.4%。术后第28天第2组受损视神经无电活动;与第1组相比,第3、4组P1潜伏期分别延长95.9%和34.9%,波幅分别下降60.9%和38.2%。各组不同时间F-VEPP1潜伏期和波幅均有明显差异(P0.05)。与第1组相比,第2、3、4组术后第14天受损侧RGC计数分别减少50.5%、34.4%和21.3%,第28天分别减少64.7%、47.6%和29.6%。各组之间受损侧RGC计数差异显著(P0.01)。结论医用生物蛋白胶可释放NGF。局部应用医用生物蛋白胶释放NGF对大鼠视神经不完全损伤疗效优于NGF肌肉注射。