iCare眼压计测量小鼠眼压值与真实眼压的相关性研究

目的：通过前房插管技术调节小鼠眼压,研究iCare眼压计测量小鼠眼压值与小鼠真实眼压之间的相关性。方法：取20只12周龄的C57BL／6J小鼠,麻醉后行前房穿刺置管,通过改变BSS液瓶高度调节其眼压。使用iCare眼压计测量其眼压值。采用SPSS软件分析iCare眼压计测量值和小鼠真实眼压之间的相关性。结果：iCare眼压计测量值与真实眼压之间相差较大,较真实眼压低约54％-71％,然而两者之间遵循如下线性回归方程：真实眼压（mmHg）=3．3988x（iCare眼压计测量值）-5．6292．r2=0．9506．P〈0．05。结论：iCare眼压计测量值较小鼠真实眼压低,然而在应用线性回归公式的情况下,iCare眼压计的测量修正值可以反映小鼠实际眼压值．     

小鼠慢性高眼压模型下视网膜神经节细胞的损伤

目的:通过巩膜外静脉烧烙术建立慢性高眼压模型,研究小鼠慢性高眼压状态下视网膜神经节细胞的凋亡情况.方法:取C57BL/6J小鼠30只.3只作为空白对照组,其余27只右眼为实验眼,左眼为对照眼.术前用iCare眼压计测量眼压,按巩膜外静脉烧烙法建立慢性高眼压模型,术后用iCare眼压计每日监测眼压.分剐取空白对照组6眼,术后1w、4 w造模成功的小鼠各8只16眼眼球,石蜡切片行Tunel法,荧光显微镜下采集图像.小鼠眼压的组间比较采用t检验.结果:给予巩膜外静脉烧烙术后1d、1w、4w小鼠慢性高眼压眼眼压(11.15±0.98、10.65±0.95、10.35±1.05)与对照眼(6.40±0.95、6.35±1.05、6.50±1.15)相比,差异有统计学意义(t=10.77～18.08,P＜0.001).Tunel法结果显示,正常小鼠空白对照组未见明显凋亡的视网膜神经节细胞.慢性高眼压组术后1w、4w可见Tunel阳性表达.而对照组术后1w及4w均未见Tunel阳性表达.结论:巩膜外静脉烧灼法能诱导出持续的肯定的小鼠慢性高眼压模型,慢性高眼压状态下小鼠视网膜神经节细胞发生凋亡,细胞凋亡是小鼠慢性高眼压状态下视网膜神经节细胞损伤的主要方式.     

4种眼压测量方法在LASIK手术前后的应用评估

LASIK手术后因角膜中央厚度、曲率和硬度都发生了明显变化,非接触式眼压计和Goldmann压平式眼压计的准确性受到了很大影响.动态轮廓眼压计由于设计原理不同,能够消除角膜厚度等因素的影响,Pentacam眼前节分析系统能用角膜厚度值对其他眼压计测量值进行校正.这2种方法能反应出真实的眼压情况.     

脉络膜脱离型视网膜脱离手术治疗前后眼压及眼轴改变的对比研究

目的：检测脉络膜脱离合并视网膜脱离患者采用不同治疗术式的术前、术后眼压及眼轴的变化,探讨眼压、眼轴与手术的相关性及两者与发病时间之间的关系。方法：收集2006年1月-2006年12月间诊断为脉络膜脱离合并视网膜脱离,并行手术治疗的患者共30例（30眼）,均为首次手术使视网膜成功复位。按照需要分组后分别在确诊后使用糖皮质激素,然后在手术前1天、术后1周、术后1个月、术后3个月及术后6个月时应用A超以及Goldmann眼压计对患者进行眼轴以及眼压的测量,并使用统计学方法进行比较。结果：1．确诊时,患者对测眼压较患侧眼压高,两者差异极显著（P〈0．01）。术前用糖皮质激素治疗7-10天后,患眼眼压值较激素治疗前明显升高（P〈0．01）。两手术组术后（玻璃体视网膜手术复位组为取硅油术后）1周、术后1月、术后3月及术后6月的眼压比术前1天眼压均显著升高（P〈0．01）;术后1月比术后1周的眼压有所降低（P〈0．05）;术后1月、3月及6月眼压之间无统计学差异（P〉0．05）。2．确诊时,患者对侧眼轴较患侧眼轴长,有统计学差异。术前用糖皮质激素治疗7～10天后,患眼眼轴较激素治疗前无统计学差异（P〉0．05）。常规视网膜手术组术后1周、术后1月、术后3月和术后6月均比术前1天延长,差异有极显著统计学意义（P〈0．01）;术后1周（29．46±2．12mm）至术后6月（28．29±2．63mm）的眼轴逐渐回缩（P〈0．01）。玻璃体视网膜手术复位组患者在硅油取出术后1周、1月、3月和6月比复位术前1天眼轴均显著延长（P〈0．01）;硅油取出术后1周（27．74±2．07rnm）至术后6月（27．72±2．17mm）时眼轴无明显改变（P〉0．05）。3．脉脱型视网膜脱离患者在确诊时双眼眼压差值与接受治疗前病程呈直线相关（r=0．833）,病程越长眼压差值越大。结论：1．脉络膜脱离型视网膜脱离患者的患眼确诊时眼压降低、眼轴缩短。2．发病时间越长,患眼眼压越低。3．患者术前应用糖皮质激素,可改善病情,提升患眼眼压。4．常规视网膜手术复位后患者眼压回升、眼轴延长,但在术后1周至术后6月内眼轴长度会有所缩短,眼压值在术后1月内也会有所回落,1个月后趋于稳定;玻璃体视网膜手术复位患者在硅油取出术后,眼压较视网膜复位术前回升、眼轴也较视网膜复位术前延长,硅油取出术后1周至6月间眼轴值无明显改变,眼压值在硅油取出术后最初1个月内有所降低,随着时间的推移趋于平稳。     

布林佐胺与噻吗洛尔滴眼液对新生血管性青光眼患者眼压及血清和房水IL-6、PEDF和VEGF水平的影响

目的:探讨布林佐胺联合噻吗洛尔滴眼液对新生血管性青光眼(NVG)患者眼压及血清和房水中白细胞介素-6(IL-6)、色素上皮衍生因子(PEDF)、血管内皮生长因子(VEGF)水平的影响。方法:选取我院2014年6月～2016年12月择期行手术治疗的86例NVG患者,按照随机数字表法均分为两组。对照组术后采取噻吗洛尔滴眼液治疗,观察组在此基础上加用布林佐胺滴眼液治疗。记录比较两组临床疗效,治疗前后眼压及血清和房水中IL-6、PEDF和VEGF水平的变化及不良反应的发生情况。结果:术后6个月,观察组总有效率为95.3%,较对照组明显升高(79.1%,P0.05)。与术前对比,两组术后7天、6个月时24 h眼压峰值、平均眼压、眼压波动值、血清和房水中IL-6、VEGF水平均显著下降(P0.01),血清和房水中PEDF水平均显著上升(P0.01),且观察组以上眼压指标较对照组同期改善更为明显(P0.01)。对照组和观察组不良反应的发生率对比差异无统计学意义(7.0%vs 11.6%,P0.05)。结论:术后应用布林佐胺联合噻吗洛尔滴眼液治疗NVG患者更能有效降低眼压和控制其波动,调节机体血管生成促进/抑制因子平衡,提高治疗效果,且安全性高。     

汉防己甲素滴眼液对高眼压模型大鼠的降眼压作用

目的比较观察汉防己甲素滴眼液与0.5%噻吗心安滴眼液对高眼压模型大鼠及正常大鼠降眼压的作用。方法正常SD大鼠共分4组：不同浓度的汉防己甲素滴眼液组（0.1%、0.2%、0.3%）及阳性对照组0.5%噻吗心安,药物滴右眼各一滴,阴性对照组生理盐水滴左眼、测量滴药前24h和滴药后1、3、6、24、48、72h的眼压。应用倍频532激光对SD大鼠右眼上巩膜静脉以及小梁网所在区域实施光凝术建立高眼压大鼠模型。高眼压模型鼠共分5组：不同浓度的汉防己甲素滴眼液0.05%、0.1%、0.2%、0.3%及阳性对照组0.5%噻吗心安,右眼即模型眼滴用药物,左眼作为空白对照。测量术前后的眼压。结果汉防己甲素滴眼液对大鼠正常眼压无降压作用（P〉0.05）。对高眼压大鼠用药后24h、72h、1周后,0.3%汉防己甲素滴眼液组降低眼压的幅度与0.5%噻吗心安滴眼液降低眼压的幅度相似（P〉0.05）;0.05%、0.1%、0.2%汉防己甲素滴眼液组也有明显的降压作用,但与0.5%噻吗心安滴眼液相比,降压幅度低于后者（P〈0.05）。结论0.05%、0.1%、0.2%、0.3%汉防己甲素滴眼液均有降低大鼠高眼压的作用,其中0.3%浓度的汉防己甲素滴眼液降眼压效果与0.5%的噻吗心安类似。汉防已甲素滴眼液作为一种治疗青光眼的药物有着良好应用前景。     

1-alpha羟化酶和人成纤维细胞生长因子-23 基因修饰小鼠离体股骨及下颌 骨X线影像的分形分析研究

目的:初步分析1-α羟化酶(1-alpha-hydroxylase,1α(OH)ase)、人成纤维细胞生长因子-23(fibroblast growth factor-23,FGF23)基因修饰小鼠离体股骨及下颌骨X线平片的分形维数(fractal dimension,FD),为其在骨质疏松症评价中的运用提供实验依据。方法:以6周龄的1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠为模型,以同龄的野生型(Wild-Type,WT)小鼠为对照,采集小鼠的股骨和下颌骨,使用离体X-射线摄影评估骨质疏松状况,利用Image J软件测量各组小鼠股骨和下颌骨X-射线影像兴趣区域的FD值,分析其差异及相关性。结果:1)与WT小鼠相比,1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠均出现骨质疏松征象,包括股骨和下颌骨骨长度及体积减少、骨密度明显下降,下颌磨牙、切牙及牙槽骨的射线透光度增高、牙髓腔宽大、根管变薄。2)1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠的股骨头和股骨远端干骺端的FD值均较WT小鼠明显增加(P<0.05),但股骨腔未见差异;下颌骨升支的FD值在1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠中明显增高(P<0.05),而在牙槽骨中未见差异;3)下颌骨升支X平片的FD值与股骨干骺端的FD值显著相关(r=0.541,P=0.049)。结论:FD值可以较好地反映骨质疏松状况,股骨干骺端、下颌骨升支是较合适的兴趣部位,分形分析可运用于下颌骨影像学的再分析。     

1-α羟化酶和人成纤维细胞生长因子-23基因修饰小鼠离体股骨及下颌骨X线影像的分形分析研究

目的:初步分析1-α羟化酶(1-alpha-hydroxylase,1α(OH)ase)、人成纤维细胞生长因子-23(fibroblast growth factor-23,FGF23)基因修饰小鼠离体股骨及下颌骨X线平片的分形维数(fractal dimension,FD),为其在骨质疏松症评价中的运用提供实验依据。方法:以6周龄的1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠为模型,以同龄的野生型(Wild-Type,WT)小鼠为对照,采集小鼠的股骨和下颌骨,使用离体X-射线摄影评估骨质疏松状况,利用Image J软件测量各组小鼠股骨和下颌骨X-射线影像兴趣区域的FD值,分析其差异及相关性。结果:1)与WT小鼠相比,1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠均出现骨质疏松征象,包括股骨和下颌骨骨长度及体积减少、骨密度明显下降,下颌磨牙、切牙及牙槽骨的射线透光度增高、牙髓腔宽大、根管变薄。2)1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠的股骨头和股骨远端干骺端的FD值均较WT小鼠明显增加(P0.05),但股骨腔未见差异;下颌骨升支的FD值在1α(OH)ase-/-、FGF23+、1α(OH)ase-/-FGF23+小鼠中明显增高(P0.05),而在牙槽骨中未见差异;3)下颌骨升支X平片的FD值与股骨干骺端的FD值显著相关(r=0.541,P=0.049)。结论:FD值可以较好地反映骨质疏松状况,股骨干骺端、下颌骨升支是较合适的兴趣部位,分形分析可运用于下颌骨影像学的再分析。     

视网膜静脉阻塞与颈动脉狭窄的相关性研究

目的:探究视网膜静脉阻塞与颈动脉狭窄的相关性研究,并为其临床检测、治疗与预后提供参考。方法:选择我院55例视网膜静脉阻塞患者(55只眼)为研究组,对其裸眼视力、矫正视力、眼压、眼底血管荧光造影(FFA)等检查资料进行分析,并进行多普勒彩超检查,记录其颈动脉狭窄情况,并对两种疾病之间的关系进行分析。同时选取55例健康人作为对照组。结果:研究组55例患者确诊为视网膜静脉阻塞(RVO),多普勒结果显示患者患侧与健侧劲动脉血流动力学各项差异不明显(P0.05);其IMT值较之对照组显著增高(P0.05);其PSV与EDV值有所降低,差异具有统计学意义(P0.05)。结论:视网膜静脉阻塞患者大多存在颈动脉狭窄,因此检测颈动脉血流动力学对于诊断与预防视网膜静脉阻塞有着重要作用。     

昆明小鼠学习记忆能力的年龄效应及其与海马突触囊泡蛋白的相关性

为了探讨昆明小鼠(Mus musculus)年龄相关性空间学习记忆能力改变及其与海马突触前囊泡蛋白1(synaptotagmin 1,SytⅠ)含量之间的关系。选取3个年龄段的昆明小鼠,①青年组:6月龄,28只;②中年组:11月龄,22只;③老年组:22月龄,17只。利用六臂辐射状水迷宫(RAWM)任务检测其空间学习记忆能力;制作组织微阵列,采用免疫组化技术检测SytⅠ在海马中的的表达;采用方差分析方法对六臂辐射状水迷宫实验参数和SytⅠ的相对含量进行统计学分析,使用Spearman秩相关检测这二者之间的相关性。结果发现,老年组昆明小鼠在学习期及记忆期的平均错误数及潜伏期均高于中年和青年鼠(P0.05),中年昆明小鼠与青年鼠之间的差异不显著(P0.05);老年组昆明小鼠在海马CA3区及齿状回(dentate gyrus,DG区)中SytⅠ的相对含量显著高于中年鼠和青年鼠(P0.05);昆明小鼠海马CA3、DG区SytⅠ的相对含量与学习期和记忆期的错误数及潜伏期均成正相关(P0.05)。由此推断,昆明小鼠可出现年龄相关性空间学习记忆能力降低,其海马CA3和DG的SytⅠ相对含量出现年龄相关性升高,海马SytⅠ升高可能与昆明小鼠年龄相关性空间学习记忆能力减退有关。     

siRNA Silencing of Gene Expression in Trabecular Meshwork: RhoA siRNA Reduces IOP in Mice

Few reports described efficient transfection in the trabecular meshwork (TM) in vivo. In the present study, we investigated the distribution of cy3-labeled siRNAs after giving injection into the anterior chamber (AC) and explored the use of RhoA siRNA (siRhoA) to modulate intraocular pressure (IOP) through downregulation of RhoA gene and protein expression. Cy3-labeled siRNAs were injected into the AC to investigate the distribution. In addition, siRhoA was applied to normal and DEX-induced elevated IOP mice. The RhoA gene was detected at 1d post-injection (PI) using real-time RT-PCR. Proteins were examined using immunofluorescence staining at 1, 2, and 3 day PI. IOP was measured pre- and post-injection using a TONOPEN. Toxicity was preliminarily assessed using clinical observation and hematoxylin-eosin staining. The study demonstrated that cy3-labeled siRNAs accumulated in mouse TM in a dose-dependent manner, with a peak at 24h PI. There was no visible siRNA fluorescence in the corneal endothelium, and little in the iris. siRhoA caused large decreases in RhoA mRNA and protein expression in mouse TM (p < 0.01). In normal mice, injections of siRhoA induced decreases in IOP, by 2d, with recovery to baseline by 3d PI. For DEX-treated animals, IOP significantly decreased from 2d to 5d PI (p < 0.05). There was no obvious toxicity after the siRhoA application. These results suggest that (1) siRNA injection into the AC leads to transient gene transfection in TM; (2) inhibiting RhoA expression in TM with siRNA is effective in suppressing elevated IOP in mice, suggesting that siRhoA is a potential pharmaceutical intervention for glaucoma.     

DBA/2J Mice Are Susceptible to Diabetic Nephropathy and Diabetic Exacerbation of IOP Elevation

Some pathological manifestations of diabetes in the eye include retinopathy, cataracts and elevated intraocular pressure (IOP). Loss of retinal ganglion cells (RGCs) in non-proliferative stages of diabetic retinopathy and small increases in IOP in diabetic patients has raised the possibility that diabetes affects the development and progression of ocular hypertension and glaucoma. The Ins2^Akita mutation is known to cause diabetes and retinopathy on a C57BL/6J (B6) background by as early as 3 months of age. Here, the impact of the Akita mutation on glaucoma was assessed using DBA/2J (D2) mice, a widely used mouse model of ocular hypertension induced glaucoma. In D2.Ins2^Akita/+ mice, the contribution of diabetes to vascular permeability, IOP elevation, RGC loss, and glaucoma development was assessed. D2.Ins2^Akita/+ mice developed a severe diabetic nephropathy and early mortality between 6–8 months of age. This agrees with previous reports showing that the D2 background is more susceptible to diabetes than the B6 background. In addition, D2.Ins2^Akita/+ mice had vascular leakage, astrocyte reactivity and a significant increase in IOP. However no RGC loss and no anterograde axonal transport dysfunction were found at 8.5 months of age. Therefore, our data show that despite severe diabetes and an increased IOP compared to controls, RGCs do not lose axon transport or degenerate. This may be due to a DBA/2J-specific genetic modifier(s) that could provide novel and important avenues for developing new therapies for diabetic retinopathy and possibly glaucoma.     

Mouse knock-out of IOP1 protein reveals its essential role in mammalian cytosolic iron-sulfur protein biogenesis

Iron-sulfur proteins play an essential role in a variety of biologic processes and exist in multiple cellular compartments. The biogenesis of these proteins has been the subject of extensive investigation, and particular focus has been placed on the pathways that assemble iron-sulfur clusters in the different cellular compartments. Iron-only hydrogenase-like protein 1 (IOP1; also known as nuclear prelamin A recognition factor like protein, or NARFL) is a human protein that is homologous to Nar1, a protein in Saccharomyces cerevisiae that, in turn, is an essential component of the cytosolic iron-sulfur protein assembly pathway in yeast. Previous siRNA-induced knockdown studies using mammalian cells point to a similar role for IOP1 in mammals. In the present studies, we pursued this further by knocking out Iop1 in Mus musculus. We find that Iop1 knock-out results in embryonic lethality before embryonic day 10.5. Acute, inducible global knock-out of Iop1 in adult mice results in lethality and significantly diminished activity of cytosolic aconitase, an iron-sulfur protein, in liver extracts. Inducible knock-out of Iop1 in mouse embryonic fibroblasts results in diminished activity of cytosolic but not mitochondrial aconitase and loss of cell viability. Therefore, just as with knock-out of Nar1 in yeast, we find that knock-out of Iop1/Narfl in mice results in lethality and defective cytosolic iron-sulfur cluster assembly. The findings demonstrate an essential role for IOP1 in this pathway.     

A role for IOP1 in mammalian cytosolic iron-sulfur protein biogenesis

The biogenesis of cytosolic iron-sulfur (Fe-S) proteins in mammalian cells is poorly understood. In Saccharomyces cerevisiae, there is a pathway dedicated to cytosolic Fe-S protein maturation that involves several essential proteins. One of these is Nar1, which intriguingly is homologous to iron-only hydrogenases, ancient enzymes that catalyze the formation of hydrogen gas in anaerobic bacteria. There are two orthologues of Nar1 in mammalian cells, iron-only hydrogenase-like protein 1 (IOP1) and IOP2 (also known as nuclear prelamin A recognition factor). We examined IOP1 for a potential role in mammalian cytosolic Fe-S protein biogenesis. We found that knockdown of IOP1 in both HeLa and Hep3B cells decreases the activity of cytosolic aconitase, an Fe-S protein, but not that of mitochondrial aconitase. Knockdown of IOP2, in contrast, had no effect on either. The decrease in aconitase activity upon IOP1 knockdown is rescued by expression of a small interference RNA-resistant version of IOP1. Upon loss of its Fe-S cluster, cytosolic aconitase is known to be converted to iron regulatory protein 1, and consistent with this, we found that IOP1 knockdown increases transferrin receptor 1 mRNA levels and decreases ferritin heavy chain protein levels. IOP1 knockdown also leads to a decrease in activity of xanthine oxidase, a distinct cytosolic Fe-S protein. Taken together, these results provide evidence that IOP1 is involved in mammalian cytosolic Fe-S protein maturation.     

A passive pressure sensor for continuously measuring the intraocular pressure in glaucomatous patients

ObjectiveThe main risk factor for the development of glaucoma, a retinal disease leading to blindness, is an increase in the intraocular pressure (IOP). Reducing this IOP can be obtained by eye drops but unfortunately the disease can still progress because IOP increases are painless, can fluctuate and, thus remain undetected during a visit to an ophthalmologist. The “MATEO” ANR project aims to develop sensors embedded in a contact lens for continuously IOP monitoring.Materials and methodsPressure sensors were produced by MEMS technology and tested with pig eyes obtained at a local slaughterhouse. Solution was injected by 50 μL steps in the eye with a Hamilton syringe while IOP was monitored in parallel with a TonoVET system and an industrial pressure transducer inserted in the injection tubing system.ResultsOur first pressure sensor prototypes were generated and inserted in a lens compatible with eye application. A wireless system was developed to excite the sensor. At same time, it was recorded the data in components inserted into spectacles and a pocket recorder. In parallel, we showed that injecting a solution in the eye anterior chamber triggered an IOP increase smaller and more stable than injections in the posterior chamber. Finally, a direct correlation was observed between IOP measured on the corneal surface with the TonoVET and the pressure transducer placed close to eye injection point.DiscussionOur results indicate that our in vitro model on pig eyes is adequate to test our new lens sensor. Finally, the pressure sensor was successfully inserted in contact lens opening the way for their in vitro and in vivo preclinical validation.     

Intraocular pressure (IOP) in relation to four levels of daily geomagnetic and extreme yearly solar activity

The link between geomagnetic field activity (GMA), solar activity and intraocular pressure (IOP) in healthy individuals was investigated. The IOP of 485 patients (970 eyes) was recorded over three nonconsecutive years (1979, 1986, 1989) which were characterized by maximal solar activity (1979, 1989) or minimal solar activity (1986). The measurements were also correlated with four categories of GMA activity: quiet (level I⁰), unsettled (II⁰), active (III⁰), and stormy (IV⁰). Participants were also differentiated by age and sex. We found that IOP was lowest on days of level IV⁰ (stormy) GMA. The drop in IOP concomitant with a decrease in GMA level was more significant during periods of low solar activity and in persons over 65 years of age. There was a trend towards higher IOP values on days of levels II⁰ and IV⁰ GMA in years of high solar activity. Differences between the sexes and among individuals younger than 65 years were not significant. Our results show an interesting aspect of environmental influence on the healthy population.     

Guanylate cyclase activators, cell volume changes and IOP reduction

Glaucoma afflicts millions of people worldwide and is a major cause of blindness. The risk to develop glaucoma is enhanced by increases in IOP, which result from deranged flow of aqueous humor. Aqueous humor is a fluid located in the front of the eye that gives the eye its buoyancy and supplies nutrients to other eye tissues. Aqueous humor is secreted by a tissue called ciliary processes and exits the eye via two tissues; the trabecular meshwork (TM) and Schlemm's canal. Because the spaces through which the fluid flows get smaller as the TM joins the area of the Schlemm's canal, there is resistance to aqueous humor outflow and this resistance creates IOP. There is a correlation between changes in TM and Schlemm's canal cell volume and rates of aqueous humor outflow; agents that decrease TM and Schlemm's canal cell volume, increase the rate of aqueous humor outflow, thus decreasing IOP. IOP is regulated by guanylate cyclase activators as shown in humans, rabbits and monkeys. There are two distinct groups of guanylate cyclases, membrane guanylate cyclase and soluble guanylate cyclase (sGC); activation of both have been shown to decrease IOP. Members of the membrane guanylate cyclase family of receptors bind to peptide ligands, while the sGC responds to gases (such as NO and CO(2)) and compounds (such as YC1, [3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole), a benzyl indazole derivative, and BAY-58-2667); activation of either results in formation of cyclic GMP (cGMP) and activation of protein kinase G (PKG) and subsequent phosphorylation of target proteins, including the high conductance calcium activated potassium channel (BKca channel). While activators of both membrane guanylate cyclase and sGC have the ability to lower IOP, the IOP lowering effects of sGC are noteworthy because sGC activators can be topically applied to the eye to achieve an effect. We have demonstrated that activators of sGC increase the rate at which aqueous humor exits the eye in a time course that correlates with the time course for sGC-induced decreases in TM and Schlemm's canal cell volume. Additionally, sGC-induced decrease in cell volume is accompanied by both K(+) and Cl(-) efflux induced by activation of K(+) and Cl(-) channels, including the BKca channel and/or K(+)Cl(-) symport. This suggests that parallel K(+)Cl(-) efflux, and resultant H(2)O efflux result in decreases in cell volume. These observations suggest a functional role for sGC activators, and suggest that the sGC/cGMP/PKG systems are potential therapeutic targets in the treatment of glaucoma.     

Muscular and intraocular pressure responses among ocular-hypertensive subjects: Is there a rationale for biofeedback?

Several animal and human investigations have indicated that intraocular pressure (IOP) levels may be associated with extreme drug-induced changes in the extraocular muscles. Further, recent data suggest that, among individuals with normal IOP level, moderate increases in facial muscle (EMG) activity around the eye while the eye is open are associated with increases in IOP. To investigate further the relationship between facial EMG activity and IOP levels and to examine a group of individuals with elevated IOP levels, subjects were recruited from outpatients at an optometry clinic. Three groups of subjects were selected: a group of ocular hypertensive subjects who showed elevated pressures at the optometry clinic and upon the day of testing, a group of labile ocular hypertensive subjects who evinced elevated pressures during their visit to the optometry clinic but lower pressures on the day of testing, and a group of normal IOP subjects who showed normal pressures both during their optometry clinic visit and on the day of testing. To investigate anxiety differences, subjects were administered the State-Trait Anxiety Inventory, but subsequent analysis revealed no group differences. To evaluate the role of stress upon muscle (EMG) functioning around the eye, subjects were subjected to imagery and standardized mental arithmetic stressors; analyses of these results also revealed no significant group differences. Finally, subjects were given EMG biofeedback for muscle activity around the eye while IOP was assessed during five alternating periods in which they made decreases and increases in EMG activity. Results revealed significant group, period, and group by period interaction effects. The pattern of results is interpreted as implicating EMG activity in IOP fluctuations; the implications of these data for potential biofeedback and stress management treatments are discussed.This research was supported by a Faculty Research Grant of the University of Alabama at Birmingham.