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Results for “RETINAL VESSELS”

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At least 613 records · Page 34Linked to original sources
PubMed1987

Adrenergic alpha 1 and alpha 2 binding sites are present in bovine retinal blood vessels.

Bovine retinal vessels have sites that specifically bind 3H-p-aminoclonidine (3H-PAC) with an apparent dissociation constant of 0.12 nM and a capacity of binding of 0.15 pmol/g. In addition, these vessels have 3H-prazosin binding sites bearing a dissociation constant of 5 nM and a binding capacity of 5 pmol/g. To understand the implications for retina-optic nerve vascular physiology and pathophysiology, studies of the exact location of the binding sites, the bioavailability of the adrenergic agonists, and the physiological responses to receptor stimulation in both normal and pathological states are required. The neural elements of the retina also have binding sites for 3H-PAC with an apparent dissociation constant of 0.38 nM in larger quantities (6.7 pmol/g tissue) than in the vascular elements. There are also binding sites for 3H-prazosin in a lower amount than in the vascular fraction (3 pmol/g tissue) with a dissociation constant of 2.4 nM. These sites are presumably related to the use of norepinephrine and dopamine as neurotransmitters by retinal neurons.

Animals↗
PubMed2000

Long-term effectiveness of photodynamic therapy by using a hydrophilic photosensitizer ATX-S10(Na) against experimental choroidal neovascularization in rats.

BACKGROUND AND OBJECTIVE: We previously demonstrated that a hydrophilic photosensitizer ATX-S10 had a potent photodynamic effect. This study was designed to reveal the long-term effectiveness of photodynamic therapy (PDT) with this agent in occluding choroidal neovascularization (CNV) and its selectivity in the neovascular tissue. STUDY DESIGN/MATERIALS AND METHODS: Experimental CNV was induced by intense photocoagulation in rat eyes. Immediately or 2 hours after intravenous injection of 8 mg/kg body weight of ATX-S10(Na), a cis isomer of ATX-S10, eyes were irradiated by a diode laser at the radiance of 3.25-65.3 J/cm(2) Vascular occlusion was identified by fundus photography, fluorescein angiography, and histology at 1, 3, 7, 14, and 28 days after PDT. As controls, non-neovascular eyes were subjected to PDT and similarly analyzed. RESULTS: By using the following treatment parameters, PDT with ATX-S10(Na) successfully occluded CNV without causing occlusion of retinal capillaries for 28 days; 7.4 and 19.6 J/cm(2) immediately after dye injection and 36.7 and 65.3 J/cm(2) 2 hours after injection. Although these conditions also caused occlusion of normal choriocapillaries and mild injuries of retinal vessels, retinal pigment epithelium, and photoreceptors at 1 day, retinal vessels and pigment epithelial cells recovered from damages by 28 days. No injuries were found in the inner retina. CONCLUSION: In optimal treatment conditions, PDT with ATX-S10(Na) can induce long-term, selective occlusion of CNV without causing irreversible damages in the inner retina.

Animals↗
PubMed2004

A model based method for retinal blood vessel detection.

Retinal blood vessels are important structures in ophthalmological images. Many detection methods are available, but the results are not always satisfactory. In this paper, we present a novel model based method for blood vessel detection in retinal images. It is based on a Laplace and thresholding segmentation step, followed by a classification step to improve performance. The last step assures incorporation of the inner part of large vessels with specular reflection. The method gives a sensitivity of 92% with a specificity of 91%. The method can be optimized for the specific properties of the blood vessels in the image and it allows for detection of vessels that appear to be split due to specular reflection.

Algorithms↗
PubMed1986

Comparison of insulin receptors from bovine retinal blood vessels and nonvascular retinal tissue.

The isolation and characterization of insulin receptors from retinal microvessels and nonvascular retinal tissue was carried out. Proteins were solubilized with Triton X-102 from retinal microvessels and nonvascular retinal tissue. The solubilized proteins were fractionated by DEAE-Sephacel ion exchange chromatography and complexed with 125I-insulin. The 125I-insulin-protein complexes were covalently cross-linked with disuccinimidyl suberate and chromatographed on a Sepharose CL-6B column. Three 125I-insulin-protein complexes with molecular weights of 560,000, 220,000 and 95,000 were obtained from both retinal microvessels and nonvascular tissue samples. The relative amount of the three complexes in retinal microvessels was about six times greater than in nonvascular retinal tissue. When aliquots of the complexes were subjected to SDS-polyacrylamide gel electrophoresis (SDS-PAGE) under non-reducing conditions, the 560,000-Da complex, which displayed the greatest specific binding of [125I]insulin, stayed at the origin; the 220,000-Da complex was dissociated into 180,000-190,000-Da and 80,000-86,000-Da components; and the 95,000-Da complex was dissociated into an 80,000-Da component. In contrast, when the cross-linked 125I-insulin-protein complexes were first reduced with dithiothreitol (DTT) and then subjected to SDS-PAGE, the 560,000-Da complex from retinal microvessels was dissociated into a 125,000-Da subunit, which is identical in size to the alpha-subunit of the insulin receptor reported in other tissues, while the 560,000-Da complex from nonvascular retinal tissue was dissociated into a 116,000-Da subunit. Upon SDS-PAGE under reducing conditions, both the 220,000-Da complex and the 95,000-Da complex from both types of retinal tissue were dissociated into 65,000-Da subunits. These results confirm that the insulin receptors of nonvascular retinal tissue exhibit structural differences from those in retinal microvessels and from insulin receptors in other tissues.

Animals↗
PubMed1988

Retinal abnormalities in Alport's syndrome.

The ophthalmological findings in 13 patients with Alport's syndrome are reported. Special attention was given to the retina and retinal functions. Flecked retinopathy was present in 12 out of the 13 cases. Two cases showed tortuosity of the retinal vessels. Retinal function tests showed no significant abnormalities. This study suggests that in Alport's syndrome, retinal lesions are more common than has been reported until now.

Adolescent↗
PubMedDate not supplied

[Retinal vasculitis in Behçet's disease].

Behçet's disease (BD) is a multisystemic disorder characterized by primary vasculitis of unknown etiology. We studied retinal vasculitis in 35 patients with ocular form of BD. All patients fulfilled the International Study Group criteria for BD. Mean age was 30.8 +/- 6.5 years (19-45 years, mean follow-up period 4.1 +/- 1.29 years (3-10 years. The disease occurred 3.3 times more often in men than in women (p = 0.0003). Retinal vasculitis was diagnosed in 26 (74.3%) of 35 patients with ocular form of BD. Retinal vascular changes characteristic of BD were bilateral in 96.1% cases and involved both arteries and veins. The earliest changes were detectable only by fluorescent angiography. Diffuse capillary leakage was observed in all cases during the active period of disease, involving the posterior pole. The disk and macular capillaries were involved most of all. Late staining of vasculature was observed in 68.6% patients. No ruptures of retinal vessels, retinal neovascularization, or areas of retinal nonperfusion were observed (except one case with occlusion of a branch of the central retinal vein), which are usually seen in other types of retinal vasculitis. Visual acuity was significantly decreased in patients with retinal occlusive vasculitis in comparison with patients without it (0.04 +/- 0.09 vs. 0.3 +/- 0.3, p = 0.029).

Adult↗
PubMed1994

Spontaneous retinal changes in Sprague Dawley rats.

Routine ophthalmological examination of over 6,000 untreated Crl:CD(SD)BR rats up to 2 years old, used in toxicologic studies from 1989 to 1992, has provided information on spontaneous retinal changes and their incidence with age. Focal linear retinopathy and coloboma were the most common findings; retinal hemorrhage, saccular aneurysm of the retinal vessels, retinal fold, absence of optic disk and retinal vascularization, and myelination of optic nerve fibers were also observed. Such accumulated data in untreated animals are of prime necessity in assessing possible drug- and chemical-induced effects on the eye after either systemic or local exposure.

Aging↗
PubMed1995

Microhemodynamics of retinal collateral vessel formation.

Retinal collaterals are a common clinical occurrence after branch vascular occlusions in humans and laboratory animals, yet the etiology and functional significance of these vessels is uncertain. A hypothesis is presented which attempts to explain the difficult problem of retinal arterial collateral circulation. This theory is consistent with microcirculatory hemodynamic research which demonstrates that microcirculatory flow determinants are primarily guided by resistance factors and vascular geometry. Testing with a simple mathematical model and SPICE simulation of a circuit model suggests this theory can be applied to cases of both arterial and venous collaterals. While the underlying determinants of flow can be described, the exact mechanisms of vascular remodelling into large caliber vessels must be primarily cellular.

Animals↗
PubMed2005

Simultaneous fluorescein and indocyanine green angiography for exudative macular degeneration.

BACKGROUND: The present study investigates how often a simultaneous fluorescein and indocyanine green (ICG) angiography had therapeutic consequences and if it is useful as a clinical routine diagnostic tool. PATIENTS AND METHODS: 502 consecutive simultaneous angiographies in eyes with exudative macular degeneration were retrospectively studied. RESULTS: A classic extra- or juxtafoveolar choroidal neovascularisation (CNV) was found in 3.5 % of the eyes. A subfoveal predominantly classic CNV was present in 19 % of the angiographies. ICG angiography showed a vascular network in 3 % of the eyes with occult CNV in fluorescein angiography. A neovascularisation supplied by retinal vessels (retinal angiomatous proliferation) was found in 9 % and a polypoidal choroidal vasculopathy (PCV) in 6 %. Other plaques or hot spots were visible in 4 %. In 11 eyes with progressive exudation from PCV and threatening of the fovea, laser treatment was successfully performed. CONCLUSIONS: Combined angiography identifies treatable PCV. Advantages of a combined procedure (easier logistics, no missing of treatable cases) and arguments for a two step procedure with ICG angiography only in selected cases (lower costs, lower rate of adverse reactions) must be weighed against each other.

Adult↗
PubMed2005

Wavelength dependence of the apparent diameter of retinal blood vessels.

Imaging of retinal blood vessels may assist in the diagnosis and monitoring of diseases such as glaucoma, diabetic retinopathy, and hypertension. However, close examination reveals that the contrast and apparent diameter of vessels are dependent on the wavelength of the illuminating light. In this study multispectral images of large arteries and veins within enucleated swine eyes are obtained with a modified fundus camera by use of intravitreal illumination. The diameters of selected vessels are measured as a function of wavelength by cross-sectional analysis. A fixed scale with spectrally independent dimension is placed above the retina to isolate the chromatic effects of the imaging system and eye. Significant apparent differences between arterial and venous diameters are found, with larger diameters observed at shorter wavelengths. These differences are due primarily to spectral absorption in the cylindrical blood column.

Algorithms↗
PubMed1995

Retinal blood vessel width measured on color fundus photographs by image analysis.

The purpose of this paper was to develop a technique using computerized image analysis to measure the width of retinal arteries and veins on color fundus photographs. The width of the retinal vessel was determined from digitized fundus photographs by programs based on edge detection and boundary tracing. The average vessel width was determined at different distances or eccentricities from the center of the optic disc and using various lengths of vessel segment. Measurements of superior and inferior temporal vessel width for 20 eyes by 2 operators showed that about 75% of the measurements could be obtained without the use of plan points. The average percent coefficient of variation of the measurements was 2.17% for 3 measurements of each vessel. This technique provides a reproducible and objective method for obtaining the following parameters: the edges of the vessel, the length of the vessel segment to be measured, location of the measurement along the vessel and subsequent retinal vessel width. This technique is readily suitable for application to clinical studies particularly clinical trials.

Adult↗
PubMed1996

Immunohistochemical characterization of developing and mature primate retinal blood vessels.

PURPOSE: To characterize developing retinal blood vessels with vascular markers and to relate the histochemical profile of maturing vessels to morphologic stages in retinal vascular development. METHODS: Vessels were examined in frozen and paraffin-embedded retinas and in wholemounts of Macaca monkeys ranging in age from fetal day 75 (F75) to adulthood. Endothelial cells were visualized immunohistochemically using antisera to von Willebrand's factor and CD31 with lectins Ulex europaeus, Bandeiraea simplicifolia, peanut agglutinin, Ricinis communis, and wheat germ agglutinin, and by ATPase and ADPase enzymatic histochemistry. Antibodies to vascular basement membrane and matrix markers laminin, fibronectin, and collagen types I and VIII, and antisera recognizing cell cycle-specific nuclear proteins (cyclin, Ki-67, Mib-1) also were used. RESULTS: Newly formed and mature vessels were reactive with reagents specific for CD31, von Willebrand's factor, types I and VIII collagens, laminin, fibronectin, U. europaeus, R. communis, and peanut agglutinin. Wheat germ agglutinin labeled vessels only after pretreatment with neuraminidase. All vascular markers appeared simultaneously, but some were distributed differentially between capillaries and larger vessels, along the central-peripheral extent of a vascular plexus, and among different vascular laminae. Markers of vessels failed to label spindle-shaped presumed vascular precursor cells lying peripheral to the advancing vessels during development. Spindle cells exhibited cyclin, Ki-67, and Mib-1 immunoreactivity. CONCLUSIONS: Immature and mature vitread and sclerad vessels displayed histochemical profiles that were qualitatively similar but that had subtle quantitative differences. Results do not support identification of spindle-shaped cells as vascular precursors in the developing monkey retina and are discussed in relation to mechanisms of retinal vascularization.

Aging↗