View clinical trials related to Regional Blood Flow.
Filter by:A number of common eye diseases such as age-related macular degeneration and glaucoma are associated with ocular perfusion abnormalities. Although this is well recognized there is not much possibility to improve blood flow to the posterior pole of the eye in these diseases. For many years, moxaverine has been used in the therapy of perfusion abnormalities in the brain, the heart and the extremities. This is based on a direct vasodilatatory effect of the drug, but also on the rheological properties of red blood cells. In a recent study the investigators have shown that intravenous moxaverine increases choroidal blood flow in healthy young subjects. The present study aims to investigate, whether moxaverine also improves blood flow in the diseased eye after systemic administration.
A number of common eye diseases such as retinal artery and vein occlusion, diabetic retinopathy, age-related macular degeneration, glaucoma and anterior ischemic optic neuropathy are associated with ocular perfusion abnormalities. Although this is well recognized there is not much possibility to improve blood flow to the posterior pole of the eye in these diseases. Since many years, moxaverine is used in the therapy of perfusion abnormalities in the brain, the heart and the extremities. This is based on a direct vasodilator effect of the drug, but also on the rheological properties of red blood cells. Whether moxaverine affects blood flow in the eye is unknown. The present study aims to investigate whether moxaverine may improves blood flow in the eye after systemic administration.
Age related macular degeneration (AMD) is a multifactorial disease with a strong genetic component. Most importantly a genetic polymorphism in the gene encoding for the complement factor H (CFH) has been recently identified which is highly associated with an increased risk of developing AMD. This Tyr402His polymorphism located on chromosome 1q31 has been implicated to play a role in the development of the disease. Given that it is known that impaired regulation of choroidal vascular tone is present in patients with AMD, the current study seeks to investigate whether the Tyr402His polymorphism is associated with altered choroidal autoregulation in healthy subjects. For this purpose a total of 100 healthy volunteers will be included in order to test the hypothesis that an impaired regulation of choroidal blood flow is present in subjects with homozygous Tyr402His variant.
Nitric oxide (NO) is a potent endothelium-derived vasodilatator that plays a major role in the control of ocular blood flow. Endothelial NO synthase (eNOS) is one of three isoforms of NOS producing NO through hydroxylation of L-arginine. The eNOS gene is located on the long arm of chromosome 7, and different polymorphic variations have been identified. These single nucleotide polymorphisms (sNP´s) have the ability to change transcription activity and therefore enzyme levels. Recent data indicate that the T -786C polymorphism (especially the homozygous variant) is associated with reduced eNOS activity and consequently impaired NO production. In the present study the investigators want to investigate if the T -786C eNOS gene polymorphism determines choroidal and optic nerve head blood flow.
After focusing many years only on intraocular pressure (IOP) as the primary risk factor, recently the impact of ocular blood flow is getting more consideration for the pathophysiology of glaucoma. The circadian change of intraocular pressure (IOP) is well investigated, but diurnal variations in ocular blood flow are yet to be evaluated, especially in glaucomatous eyes. This study is performed to investigate circadian variation of ocular blood flow assessed by laser interferometric fundus pulsation amplitude (FPA) and laser Doppler flowmetry (LDF) in glaucomatous eyes during topical antiglaucoma therapy at 8:00, 12:00, 17:00 and 21:00, to compare these circadian variation of ocular blood flow in glaucomatous eyes with variations in healthy eyes and to relate blood flow variations with IOP variations.
It is the study aim to investigate the effect of glp-2 on blood flow in humans. we wish to study eventual changes in renal blood flow, carotic blood flow and cardiac out put. GLP-2 will be administered subcutaneously, and the effect monitored by doppler ultra sound scannings and cotinuesly measuring of cardiac out put and blood pressure. The study will include 15 healhty volunteers, 10 wil receive 450 nmol GLP-2 and 5 will receive 1 ml of isotonic saline (as baseline reference).
A couple of studies have shown that illuminating the eye with diffuse flickering light is accompanied by an increase of retinal vessel diameters, optic nerve head blood flow and retinal blood flow. We have recently used this visual stimulation technique as a new and powerful tool for the non-invasive investigation of vascular reactivity. Additionally, we could show that this response is diminished in patients with vascular pathologies and that the response is dependent on nitric oxide, indicating that flicker induced vasodilatation may reflect endothelial dysfunction and may be a new approach to test endothelial function in vivo. One of the most widely used method for the assessment of endothelial function is flow mediated dilatation (FMD). FMD has been shown to give a reliable estimate of vascular function in vivo. In the present study, we set out to compare the standard method for the evaluation of endothelial function, FMD, to flicker induced vasodilatation in the retina.
Oxidative stress, which refers to cellular damage caused by reactive oxygen intermediates, has been implicated in many disease processes, especially age-related disorders. Many trials investigating use of antioxidants in protecting different tissues against oxidative stress have been conducted, but the results are ambiguous. Inflammation is generally associated with enhanced oxidative stress and widespread endothelial dysfunction. In the present study, the infusion of LPS, which is a cell wall component of Gram-negative bacteria and a major mediator in the pathogenesis of septic shock, will be used as a standardized experimental model of systemic inflammatory response in humans. The assessment of outcome parameters will include measurements of ocular blood flow, forearm blood flow and plasma concentration of cytokines. Measurements of ocular hemodynamics provide an unique chance to investigate local blood flow in humans non-invasively. Moreover, the retina is especially susceptible to oxidative stress because of its high consumption of oxygen, its high polyunsaturated fatty acid content, and its exposure to visible light. Evidence from literature clearly supports a role for oxidative stress in pathophysiology of several ocular diseases including diabetic retinopathy and age-related macular degeneration. To investigate the retinal vascular reactivity we will use systemic hyperoxia as a stimulus. The measurement of forearm blood flow will be use to assess endothelial function. The main study objective is to investigate the effect of oral vitamins and minerals supplementation on impaired retinal vascular reactivity after LPS administration.
There is evidence from a variety of animal studies that choroidal blood flow is under neural control. By contrast, only little information is available from human studies. Recent results indicate that a light/dark transition is associated with a short lasting reduction in choroidal blood flow. We have shown that during unilateral dark/light transition both eyes react with choroidal vasoconstriction strongly indicating a neural mechanism. The present studies investigate this possibility by using pharmacological interventions. The pharmacological agents tested include a nitric oxide synthase inhibitor, an alpha-receptor agonist (as a control substance for the blood pressure increasing nitric oxide synthase inhibitor), a muscarinic receptor blocker, and a non-specific beta-blocker. These drugs were chosen on the basis of previous animal experiments, as the systems, which are specifically influenced by these substances, are likely involved in neural control of choroidal blood flow.
Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Previous findings suggest endothelial dysfunction in glaucomatous optic neuropathy, in particular alterations in endothelin- and nitric oxide- system, which both play an important role in local regulation of vascular tone. In the present study, changes in ocular perfusion pressure will be performed during administration of drugs, which may potentially alter the pressure-flow relationship. These drugs include endothelin-1 and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).