A computational study targeting the mutated L321F of ERG11 gene in C. albicans,associated with fluconazole resistance with bioactive compounds from Acacia nilotica

BackgroundEmergence of fluconazole resistance mediated by L321F mutation in the ERG11 gene poses a serious impediment in the candidal treatment process. This leads to the search of novel target proteins to develop newer drugs against fluconazole resistant C. albicans. The present investigation is thus aimed to explore the inhibitory potential of bioactive compounds from A. nilotica against the wild and mutated ERG11 gene of C. albicans.Materials and methodsHomology modelling of the wild and mutated ERG11 target gene was done by Modeller 9.2, with SDM I-mutant form of ERG11 together with SAVES server and Ramachandran plot validation. 2D and 3D structures of the bioactive compounds from A. nilotica were optimized by ACD chemsketch. Molinspirational assessments for the molecular properties of the ligands and their drug likeliness were estimated. In silico inhibitory potential of the selected ligands against wild and mutated ERG11 was done by AutoDock 2.0 and was visualized with Accelrys discovery studio tool.ResultsApigenin proved to be the best candidate to target mutant ERG11 with a binding energy of −8.33 Kcal/mol followed by catechin with six hydrogen bonds with more drug likeliness. Molinspiration assessments showed zero violations for all the bioactive compounds from A. nilotica and the TPSA scores of the ligands showed the values < 140 Å towards the best oral bio-availability.ConclusionThe findings of the study emphasize that kaempferol, apigenin and catechin from A. nilotica seem to possess a promising inhibitory effect against the wild and mutated ERG11 of C. albicans suggesting ERG11 as the best target to combat fluconazole resistant C. albicans with further in vivo validation targeting the same.     

Specific deficits in visual electrophysiology in a mouse model of dominant optic atrophy

Autosomal dominant optic atrophy (ADOA) is a slowly progressive optic neuropathy caused by mutations in the OPA1 gene. OPA1 is ubiquitously expressed and plays a key role in mitochondrial fusion. Heterozygous Opa1 mutant mice (B6; C3-Opa1^Q285STOP), have previously been reported to develop visual defects and optic nerve changes. In this study, in vivo visual electrophysiological testing (ERGs and VEPs) was performed on 11–13 month old B6; C3-Opa1^Q285STOP mice (n = 5) and age/sex matched wildtype littermate controls. Full intensity series were recorded in response to brief (4 ms) single flash stimuli delivered in a Ganzfeld dome under dark- and light-adapted conditions. The major ERG components (a-wave and b-wave) showed no detectable difference from wildtype in the amplitude or implicit time of dark-adapted ERGs across the full intensity range tested. This was also true for the components of the dark-adapted VEP. However, the light-adapted ERG responses revealed a significant reduction in the photopic negative response (PhNR) amplitude in Opa1^+/− animals relative to wildtypes at the brighter intensities tested. Elements of the light-adapted VEP were also abnormal in mutant mice. Overall Opa1^+/− mice display functional deficits in electrophysiology that are consistent with ganglion cell dysfunction. These deficits may correlate with a reduction in the dendritic arborisation of retinal ganglion cells, which has been previously reported to occur at a similar age in the same mutant mouse line (Williams et al., 2010). The functional phenotype we have described in this mouse model may be useful in the robust and accurate assessment of potential treatments for ADOA.     

Spatial tuning of the pattern ERG across temporal frequency

The spatial response function of the electroretinogram (ERG) to contrast checkerboard pattern reversal at several check sizes was determined at a fixed contrast. The influence of the rate of modulation on the spatial response function was assessed: Reversing square wave patterns were presented at eight temporal frequencies ranging from 1 to 25 reversals per sec; The waveform consisted of an initial positive and a subsequent negative deflection. Irrespective of the temporal frequency, the spatial response function of the positive component did not show a spatial tuning. The amplitude of the negative component exhibited a pronounced attenuation of the response at check sizes larger than optimal. Mean maximal amplitude was found at an optimal check size between 25 and 50 min of arc. A distinction between a positive or negative component was not made for temporal frequencies higher than 10 reversals per sec, since the wave-form at these modulation rates consisted merely of a sinusoidal steady-state response. The spatial response function obtained at 14 reversals per sec; resembling that of the negative component, exhibited a prominent spatial tuning. The results demonstrate that the pattern ERG has at least two components: a positive component which is not specific to changes in retinal distribution of contrast, followed by a negative wave showing spatial tuning across temporal frequency.     

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.     

Comparison of focal macular cone ERGs in complete-type congenital stationary night blindness and APB-treated monkeys

Focal macular cone electroretinograms (ERGs) and multifocal ERGs were recorded to study the macular function in patients with the complete-type of congenital stationary night blindness (cCSNB). The waveforms of the focal macular cone ERGs and the on- and off-responses of the multifocal ERGs in the cCSNB patients were similar to those recorded from monkey retinas treated with L-2 amino-4-phosphonobutyric acid (APB), suggesting that patients with cCSNB have a complete defect of the on-pathway even in the central retina. The results also demonstrated that there was a paradoxical positive response in the central retina of cCSNB patients, as compared to the negative full-field ERGs in the same subjects.     

老年黄斑变性的多焦ERG检测

目的：运用多焦视网膜电图（electroretinography,ERG）评价老年黄斑变性（age-related macular degeneration,AMD）患者的局部视网膜功能。方法：采用103个六边形刺激图形，记录12例（24只眼）AMD患者在4分钟记录时间内的多焦ERG波形图及三维功能图。结果：AMD患者总体ERG的a波、b波振幅在正常范围内，而1环及2环a波、b波振幅下降。三维图显示中央局部视网膜功能降低。结论：多焦ERG是一种评价局部视网膜功能的新技术，可用于眼底病的早期诊断。     

m-ERG-阶kernel反应对青光眼的诊断价值

目的:应用多焦视网膜电图(m-ERO)一阶kemel反应(FOK),检测青光眼视功能损害,评价其在青光眼中的诊断价值及其与视野、视盘改变的相关性.方法:根据1987年全国青光眼协作组拟定的标准,并结合视野选择了42只青光眼和16只可疑青光眼共58只眼,分为早期、中期、晚期青光眼和可疑青光眼四组,同时选择了33只正常眼,检测m-ERG的FOK P波、N波的振幅和峰时,并进行统计学处理.结果:观察了四组青光眼与正常对照组的m-ERG的FOK,结果显示,1、FOK的P波振幅、N波振幅、N波峰时,在正常对照组与三个青光眼组间有显著性差异(P＜0.05),与可疑组间无显著性差异(P＞0.05).P波峰时在正常对照组与其它组间无显著性差异(P＞0.05),但其在鼻上、鼻下、颞下三个象限正常对照组与各期青光眼组有显著性差异(P＜0.05).2、FOK的异常检出率(敏感性)分别在早、中、晚期,可疑青光眼组和正常对照组,P波振幅的敏感性分别为73.3%,62.5%,100%,62.5%.特异性为72.7%,N波振幅的敏感性分别为66.7%,56.3%,90.9%,50%,特异性为63.6%.P波峰时的敏感性分别为73.3%,100%,90.9%,43.8%,特异性为51.5%,N波峰时的敏感性分别为53.3%,50%,90.9%,43.8%,特异性为54.5%.3、FOK的P波,N波的振幅与MD呈负相关(P＜0.05),N波的峰时与MD呈正相关(P＜0.05),P波的峰时与MD相关性不大(P＞0.05).4、FOK的P波振幅、N波振幅与C/D呈负相关(P＜0.05),N波峰时与C/D呈正相关(P＜0.05),P波峰时与C/D相关性不大(P＞0.05). 结论:1、在本文记录参数的条件,m-ERG提供了评价育光眼视功能损害的一种敏感的方法,早期青光眼中m-ERG的FOK振幅和峰时的敏感性均达60%左右,对可疑青光眼,FOK的振幅的敏感性也可达50%左右.2、随着青光眼视功能损害的加重,m-ERG的敏感性逐渐升高,晚期青光眼,m-ERG的FOK振幅和峰时的敏感性达90%以上.3、M-ERG FOK的振幅与MD、C/D呈负相关,N波峰时与MD、C/D里正相关,P波峰时与MD、C/D相关性不大.4、m-ERG的特异性还不够高,尚未发现具有典型特征性的m-ERG改变.因而在临床上应该是多种检测指标联合观测,以提高诊断的敏感性、特异性.     

ERG甲基化作为无创产前诊断唐氏综合征标记的可行性研究

目的探讨ERG基因是否可以作为孕早期血浆中检测胎儿DNA的通用标志物。方法随机选择早期妊娠孕妇70例,并以经体检确定为未孕健康妇女70例、分娩过21-三体胎儿的妇女11例和顺产后3 d妇女20例作为对照组。利用甲基化敏感限制性内切酶HpaⅡ、MspⅠ酶切后进行常规PCR的方法,检测血细胞、绒毛和血浆DNA目的基因ERG21-128序列的甲基化模式,并对妊娠组和对照组样本进行统计学分析。结果位于21号染色体上的ERG基因21-128序列在70例孕8、9、10周孕妇绒毛组织中甲基化而在母体血细胞中未甲基化,绒毛甲基化检出率为100%;在血浆中游离胎儿DNA ERG基因21-128序列的甲基化检出率为77.1%,敏感度为77.1%。其中8、9、10周甲基化差异无统计学意义（P〉0.05）。在70例未孕健康妇女、11例生产过21三体胎儿的健康妇女和20例产后3 d妇女的对照组的血浆中ERG 21-128序列均未甲基化。结论在母体和胎儿DNA中,ERG基因21-128区的甲基化有显著性差异,实验方法也比较简单,提示了ERG是无创性产前诊断DS的一个潜在标记物。