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Retinal Blood Vessels (retinal + blood_vessel)
Selected Abstracts4144: Retinal blood vessel phenotyping in miceACTA OPHTHALMOLOGICA, Issue 2010J RUBERTE Purpose In the retina there is a compromise between optimal visual function and optimal oxygenation. Retinal blood vessels have a relative sparse distribution and their size is small in order to minimise optical interference with the light path. Hence, the blood flow volume in the retina is relatively low. This fact, together with the high oxygen consumption of the retinal tissue, could facilitate the development of retinal hypoxia and subsequent retinopathy when the vascular bed is altered. Thus, the analysis of retinal blood vessel must be a crucial step during retinal phenotyping in mutant mice. Methods Different technologies and methods have been used in order to analyze structure, distribution and function of retinal blood vessels, among others: retinal digest preparations, retinal whole mount immunohistochemistry, transmission and scanning electron microscopy, fluorescein and Mercox vascular injections and scanner laser ophthalmoscopy. Results In our laboratory, morphological and topographic alterations of retinal blood vessels in Bmi1 and Sirt1 knockout mice, as well as in IGF-1 and IL-10 transgenic mice, have been observed and documented Conclusion The mouse genome is fully sequenced. 99% of the coding genes present in man are also present in mouse. Moreover, the majority of disease-related genes have been conserved since the emergence of the bony fishes about 400 million years ago. These facts and the development during the last two decades of an extensive toolbox to study the functional effects of genetic variation in mice, make them the ideal model organism for the study of human eye diseases. In this sense, morphological and functional analyses of retinal blood vessel in mutant mice could help to understand vascular gene-based mechanisms that lead to retinopathy [source] Augmentation of a nearest neighbour clustering algorithm with a partial supervision strategy for biomedical data classificationEXPERT SYSTEMS, Issue 1 2009Sameh A. Salem Abstract: In this paper, a partial supervision strategy for a recently developed clustering algorithm, the nearest neighbour clustering algorithm (NNCA), is proposed. The proposed method (NNCA-PS) offers classification capability with a smaller amount of a priori knowledge, where a small number of data objects from the entire data set are used as labelled objects to guide the clustering process towards a better search space. Experimental results show that NNCA-PS gives promising results of 89% sensitivity at 95% specificity when used to segment retinal blood vessels, and a maximum classification accuracy of 99.5% with 97.2% average accuracy when applied to a breast cancer data set. Comparisons with other methods indicate the robustness of the proposed method in classification. Additionally, experiments on parallel environments indicate the suitability and scalability of NNCA-PS in handling larger data sets. [source] Regression of Alterations in Retinal Microcirculation Following Treatment for Arterial HypertensionJOURNAL OF CLINICAL HYPERTENSION, Issue 8 2006Antonio Pose-Reino MD Evaluation of early hypertension-related alterations in retinal microcirculation has been subjective and poorly reproducible. The authors recently described a semiautomatic computerized system for evaluation of the calibre of retinal blood vessels that has shown very good reproducibility. In the study, this system was used to measure the calibres of retinal arterioles and veins, and their ratio, in a group of 51 hypertensive outpatients before and after 6 months of treatment with losartan or, if required for satisfactory blood pressure control, losartan plus hydrochlorothiazide. Mean retinal arteriole diameter increased from 0.0842±0.003 mm to 0.0847±0.003 mm (p=0.001). Arteriovenous ratio increased from 0.753±0.03 to 0.756±0.03 (p=0.005). This observation suggests regression of early hypertension-related alterations in retinal microcirculation after 6 months of antihypertensive treatment. [source] Architecture of cannabinoid signaling in mouse retinaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 18 2010Sherry Shu-Jung Hu Abstract Cannabinoid receptors and their ligands constitute an endogenous signaling system that is found throughout the body, including the eye. This system can be activated by ,9 -tetrahydrocannabinol, a major drug of abuse. Cannabinoids offer considerable therapeutic potential in modulating ocular immune and inflammatory responses and in regulating intraocular pressure. The location of cannabinoid receptor 1 (CB1) in the retina is known, but recently a constellation of proteins has been identified that produce and break down endocannabinoids (eCBs) and modulate CB1 function. Localization of these proteins is critical to defining specific cannabinoid signaling circuitry in the retina. Here we show the localization of diacylglycerol lipase-, and -, (DGL,/,), implicated in the production of the eCB 2-arachidonoyl glycerol (2-AG); monoacylglycerol lipase (MGL) and ,/,-hydrolase domain 6 (ABHD6), both implicated in the breakdown of 2-AG; cannabinoid receptor-interacting protein 1a (CRIP1a), a protein that may modulate CB1 function; and fatty acid amide hydrolase (FAAH) and N -acylethanolamine-hydrolyzing acid amidase (NAAA), which have been shown to break down the eCB anandamide and related acyl amides. Our most prominent finding was that DGL, is present in postsynaptic type 1 OFF cone bipolar cells juxtaposed to CB1 -containing cone photoreceptor terminals. CRIP1a is reliably presynaptic to DGL,, consistent with a possible role in cannabinoid signaling, and NAAA is restricted to retinal pigment epithelium, whereas DGL, is limited to retinal blood vessels. These results taken together with previous anatomical and functional studies define specific cannabinoid circuitry likely to modulate eCB signaling at the first synapse of the retina as well as in the inner plexiform layer. J. Comp. Neurol. 518:3848,3866, 2010. © 2010 Wiley-Liss, Inc. [source] 3252: Basic mechanisms and factors influencing the neurovascular coupling in the eyeACTA OPHTHALMOLOGICA, Issue 2010G GARHOFER Neuro-vascular coupling is a basic physiological mechanism in the eye that allows for adapting retinal and optic nerve head blood flow to changing metabolic demands, induced by an increase in neural activity. Despite many efforts, the mechanisms that leads to this coupling process are largely unknown. Among others, nitric oxide seems to play an important role in the vasodilatory answer. It has been shown that the unspecific blockade of nitric-oxide syntheses leads to a pronounced reduction of flicker induced vasodilatation in healthy subjects. This indicates that nitric oxide plays an important role in this signaling cascade. Additionally, there is evidence that astrocytes act as a mediator between ganglion cells and blood vessels in the retina. This hypothesis is strengthened by the observation that the presence and distribution of retinal astrocytes correlates with the presence and distribution of retinal blood vessels. This talk will summarize the concept of neuro-vascular coupling in the eye and give an overview about our current understanding of the mechanisms and factors involved in this process. [source] 4144: Retinal blood vessel phenotyping in miceACTA OPHTHALMOLOGICA, Issue 2010J RUBERTE Purpose In the retina there is a compromise between optimal visual function and optimal oxygenation. Retinal blood vessels have a relative sparse distribution and their size is small in order to minimise optical interference with the light path. Hence, the blood flow volume in the retina is relatively low. This fact, together with the high oxygen consumption of the retinal tissue, could facilitate the development of retinal hypoxia and subsequent retinopathy when the vascular bed is altered. Thus, the analysis of retinal blood vessel must be a crucial step during retinal phenotyping in mutant mice. Methods Different technologies and methods have been used in order to analyze structure, distribution and function of retinal blood vessels, among others: retinal digest preparations, retinal whole mount immunohistochemistry, transmission and scanning electron microscopy, fluorescein and Mercox vascular injections and scanner laser ophthalmoscopy. Results In our laboratory, morphological and topographic alterations of retinal blood vessels in Bmi1 and Sirt1 knockout mice, as well as in IGF-1 and IL-10 transgenic mice, have been observed and documented Conclusion The mouse genome is fully sequenced. 99% of the coding genes present in man are also present in mouse. Moreover, the majority of disease-related genes have been conserved since the emergence of the bony fishes about 400 million years ago. These facts and the development during the last two decades of an extensive toolbox to study the functional effects of genetic variation in mice, make them the ideal model organism for the study of human eye diseases. In this sense, morphological and functional analyses of retinal blood vessel in mutant mice could help to understand vascular gene-based mechanisms that lead to retinopathy [source] 2324: Comparison of algorithms for oximetry in vivo and ex vivoACTA OPHTHALMOLOGICA, Issue 2010D DE BROUWERE Purpose Several authors have proposed a number of algorithms to extract the oxygen saturation in retinal blood vessels based on multispectral image analysis. We evaluated the outcomes of seven known algorithms based on hyperspectral retinal images. Methods Hyperspectral images are acquired using a fundus camera where a slit spectrograph is registered onto a retinal image. This combination compromises both accurate spatial and spectral information over the selected slit. Hyperspectral image analysis was used as input for the oximetry calculations described in the literature. We used a model eye to evaluate the different techniques in a controlled setup. Defibrinated horse blood was perfused through microtubules placed in front of a white (spectralon) background. Oxygen saturation was controlled by mixing different concentrations of sodium dithianate in the blood. Results Oxygen saturation was varied in five equidistant steps between 0 and 1. We correlated the outcomes to the metric of Harvey et al. [Biomed Optics 6631, 2007] Linear correlation with other algorithms resulted in r2 values between 0.881 and 0.985, however we observed a large discrepancy of the slope of each correlation line. The algorithms were also evaluated in images recorded in five healthy volunteers. In all techniques, veins could be separated from arteries by their reduces oxygen saturation, although values varied strongly between the different techniques. Conclusion Our findings confirm the working of a number of noninvasive retinal oximetry algorithms. Different readings can be can be attributed to an offset caused by an uncertainty of pigmentation and scattering parameters in the calibration procedure. [source] Clinical and histological findings after intravitreal injection of bevacizumab (Avastin®) in a porcine model of choroidal neovascularizationACTA OPHTHALMOLOGICA, Issue 3 2010Nathan Lassota Abstract. Purpose:, To examine the effect of intravitreally injected bevacizumab (Avastin®) on the histological and angiographic morphology of choroidal neovascularization (CNV) in a masked and placebo-controlled animal study. Methods:, Choroidal neovascularization was induced surgically in 11 porcine eyes by perforating Bruch's membrane with a retinal perforator. After closure of the ports used for the vitrectomy, which was performed to facilitate the Bruch's membrane rupture, 0.05 ml of either bevacizumab or Ringer-Lactat (placebo) was injected into the vitreous cavity. Eyes were enucleated after 14 days. Fundus photographs and fluorescein angiograms (FAs) were obtained immediately prior to enucleation. Sections of formalin- and paraffin-embedded eyes were examined by light microscopy and by immunohistochemical staining. Results:, Placebo-injected eyes exhibited the highest propensity to leak, with five of six eyes leaking on FA, whereas only one of five bevacizumab-injected eyes exhibited leakage. On histological examination, all 11 eyes contained CNV membranes of similar size, regardless of treatment. The number of vascular endothelial cells was significantly reduced (p = 0.03) in CNV membranes from eyes that had been injected with bevacizumab when compared with CNV membranes from placebo-injected eyes. There was a trend towards more retinal pigment epithelium cells (p = 0.16) and fewer glial fibres (p = 0.08) in membranes from bevacizumab-treated eyes compared with placebo-treated eyes. Bevacizumab was identified immunohistochemically in the inner limiting membrane (ILM) and to a lesser degree in the remaining retina. Strong staining was also detected in both retinal blood vessels and entire CNV membranes with no cellular predisposition. Vascular endothelial growth factor expression was found in the CNV membranes, in the ILM, in the ganglion cell layer, in Müller cells throughout the neuroretina and in retinal blood vessels. Conclusions:, Bevacizumab significantly reduced the proliferation of vascular endothelial cells in CNV membranes and showed a strong trend towards a reduction of leakage from these membranes. After a single injection, bevacizumab did not exhibit a size reducing effect on CNV, but it was still present in the membranes 14 days after intravitreal injection. [source] Noninvasive oximetry and glaucomaACTA OPHTHALMOLOGICA, Issue 2009OB OLAFSDOTTIR Purpose To investigate retinal vessel oxygen saturation in relation to glaucomatous visual field damage. Specifically, we examined whether oxygen saturation in retinal blood vessels differs between regions corresponding to glaucomatous visual field defects compared to regions without visual field defects. Methods A spectrophotometric retinal oximeter (Oxymap ehf, Reykjavík, Iceland) was used to measure oxygen saturation in retinal arterioles and venules. The oximeter consists of a fundus camera, beam splitter, light filters and software that evaluate the oxygen saturation. The glaucomatous defect was estimated from a visual field test using the Octopus 1-2-3 perimeter. One eye in 13 individuals with open angle glaucoma with or without pseudoexfoliation syndrome was examined. Results In retinal areas with no visual field defect, the mean oxygen saturation in arterioles was 102±6% and 65±9%, (mean±SD) in venules. The arteriovenous difference was 37±10%. In retinal areas corresponding to visual field defects, the mean oxygen saturation in arterioles was significantly lower; 98±5% (p=0.04, paired t-test, n=13). The venules were at 68±7% (p=0.3) and the arteriovenous difference was also significantly lower; 30±10% (p=0.04). Conclusion Arteriolar oxygen saturation and arteriovenous difference is statistically lower in areas with visual field defects compared to areas without visual field defects. This data suggests that visual field defects are associated with a reduction in retinal oxygen delivery and metabolism. [source] Recent developments in retinopathy of prematurityACTA OPHTHALMOLOGICA, Issue 2009B MORTEMOUSQUE The retinopathy remains the principal severe ophthalmologic complication of neonates with a gestationalage of 32 weeks or less. It's a major cause of lifelong blindness beginning in infancy. As many other ocular pathologies, including diabetic retinopathy, and age-related macular degeneration, result in vision loss because of aberrant neoangiogenesis. A common feature of these conditions is the presenceof hypoxic areas and overexpression of the proangiogenic vascular endothelialgrowth factor (VEGF). Its prevantion can be made by a better management of the oxygenation of these children but also by a better knowledge of the other risk factors. The prevailing current treatment, laser ablation of the retina, is destructive and only partially effective. Preventive and less destructive therapies are much more desirable. So, Angiogenesis, or the formation of new retinal blood vessels is a key feature of many proliferative retinal diseases including diabetic retinopathy,retinal vein occlusions, and retinopathy of prematurity. [source] Clinical and Histological Aspects of CNV Formation: Studies in an Animal ModelACTA OPHTHALMOLOGICA, Issue thesis2 2008Nathan Lassota MD Abstract. The purpose of the present thesis was to develop an animal model of CNV in order to study the early formation of CNV and to test the effects of an anti-angiogenic treatment. Porcine eyes were chosen as a substrate for CNV induction, since they are similar to human eyes in terms of both macroscopic and microscopic morphology. However, a major difference is that pigs lack a fovea; instead they have a visual streak, with a relatively stable and high concentration of cones. By surgical perforation of Bruch's membrane we were able to induce formation of CNV membranes. The morphology and cellular composition of these membranes varied with the surgical technique employed. When RPE cells were locally removed at the time of perforation, the resulting CNV was thinner, contained fewer blood vessels and was less prone to leak on fluorescein angiography than when RPE cells were left intact at induction. The neuroretina overlying the perforation site was not damaged by any of the surgical techniques, thus allowing the subsequent retinal damage to be ascribed to the actual process of CNV formation. Using this animal model allowed us to directly map histological findings onto fluorescein angiograms and thereby perform meaningful correlations between histopathologic and photographic features. Such correlations have been hampered in human subjects, since human eyes are not enucleated as a consequence of CNV and are therefore only available for post-mortem studies. In such studies there often is a considerable time-gap between the death of the patient and the latest available fluorescein angiogram, thereby allowing macular pathology to evolve in the interim. Histological examination of the porcine membranes demonstrated that they were composed of RPE cells, glial cells, macrophages, endothelial cells, collagen and smooth muscle fibres, which are the same cellular and fibrillar elements that dominate human CNV membranes. The porcine model was applied to test the effects, in a randomized and masked fashion, of intravitreally injected bevacizumab. Bevacizumab, a pan VEGF A antibody, was found to reduce both the proliferation of endothelial cells in CNV membranes and the propensity to leak in fluorescein angiograms. Immunohistochemically, bevacizumab was detected in the inner limiting membrane, in retinal blood vessels and binding uniformly to the entire CNV membrane without any cellular predisposition. Based on the above findings we believe that the porcine CNV model shows a bearing to human disease and therefore might be used as a tool to obtain improved treatments for this debilitating condition. [source] | ||||||||||