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PubMedDate not supplied

In vivo use of oligonucleotides to inhibit choroidal neovascularisation in the eye.

BACKGROUND: We have previously demonstrated the in vivo uptake of oligonucleotides in the rat eye and have continued with experiments to look at the effectiveness of targeted oligonucleotide sequences. Vascular endothelial growth factor (VEGF) is correlated with new blood vessel formation and has been implicated in numerous eye diseases characterised by abnormal blood vessel proliferation. An oligonucleotide targeted to the VEGF sequence was examined for its effect on VEGF production in vitro and the development of choroidal neovascularisation in vivo in the eye. METHODS: A series of sequences were assessed in an in vitro screening system using retinal pigment epithelial (RPE) cells to demonstrate a reduction in VEGF. A targeted sequence was further investigated using an animal model of choroidal neovascularisation where a krypton laser was used to produce a wound healing response in the choroid and retina. The oligonucleotide was injected into the vitreous and the development of choroidal neovascularisation assessed using fluorescein angiography. RESULTS: The targeted sequence was shown in vitro to downregulate the VEGF produced by RPE cells grown under hypoxic conditions and when injected into laser treated eyes was shown to be preferentially taken up in the laser lesion. Fluorescein angiography demonstrated that the test oligonucleotide was successful in reducing laser-mediated choroidal neovascularisation. CONCLUSIONS: A sequence corresponding to the 5'UTR of the VEGF gene has provided encouraging results for the treatment of neovascularisation.

Animals↗
PubMed2002

Some observations of the structure of the choroid plexus and its cysts.

The structure of the choroid plexus was studied in five normal human embryos, three normal fetuses and three fetuses with choroid plexus cysts. These were detected by ultrasound and the fetuses were karyotypically normal. The choroid plexus appears in the lateral cerebral ventricles at the seventh developmental week. The early structure is lobulated with vessels running in the mesenchymal stroma and forming capillary nets under the single-layered ependymal epithelium. This embryonal structure is converted into the fetal type during the ninth developmental week as the embryonal capillary net is replaced by elongated loops of wavy capillaries that lie under regular longitudinal epithelial folds. The choroid plexus cysts exhibited accumulation of fluid within distended mesenchymal stroma and did not show the wavy folds on this surface, which was smooth. Within this connective tissue of the cyst wall were distended angiomatous interconnecting thin-walled capillaries. Therefore, filled cavities were not lined by any epithelium. We suggest that fetal choroid plexuses cysts (at least in many cases) are in fact pseudocysts exhibiting angiomatous patterns of capillaries in their walls.

Capillaries↗
PubMed1994

Choroidal myogenic autoregulation and intraocular pressure.

This study tests the hypothesis that choroidal myogenic autoregulation participates in the intraocular pressure (IOP) response to mean arterial pressure (MAP) by minimizing arterial-pressure-dependent changes in choroidal blood volume. To test this hypothesis, the IOP response to MAP was quantified before and after impairing choroidal autoregulation. In a previous study, the efficacy of choroidal myogenic autoregulation was inversely related to IOP. Therefore, in one series of experiments (n = 6), the relationship between MAP and IOP was determined at normal and elevated baseline IOP (i.e., 15 and 25 mmHg, respectively). In a second series of experiments (n = 6), the relationship between MAP and IOP was determined at the normal IOP (15 mmHg) before and after administering hydralazine, an arterial vasodilator. In both series, the MAP manipulations were kept brief to avoid the confounding effects of aqueous compensation. The experiments were performed in pentobarbital anesthetized rabbits with hydraulic occluders placed on the thoracic descending aorta and inferior vena cava to raise and lower MAP, respectively. MAP was measured via a central ear artery catheter. The right eye was cannulated with two 23 gauge needles; one cannula was used to set the IOP by varying the ocular volume and the other was used to measure the IOP. The protocol consisted of inflating the occluders to cause brief (1-1.5 min) ramp increases and decreases in MAP over a wide pressure range. Baseline IOP was set prior to each occlusion, but was otherwise uncontrolled. In the first series, the MAP range was 30 to 95 mmHg and IOP changed by 6 mmHg at the normal baseline IOP and by 18 mmHg at the elevated baseline IOP. The corresponding volume shifts were 7.7 and 14.5 microliters, respectively. In the second series, the MAP range was 25 to 95 mmHg and IOP changed by 6 mmHg during control and by 14 mmHg after hydralazine. The corresponding volume shifts were 6.7 and 13.8 microliters, respectively. In both series, the prompt return of IOP to baseline upon restoration of normal MAP indicated that the volume changes were due to changes in ocular blood volume. Additional experiments confirmed that elevating the baseline IOP and administering hydralazine impaired choroidal autoregulation but did not alter the cranial venous pressure response to varying MAP.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Embryonic rabbit retinal transplants survive and differentiate in the choroid.

Retinal allotransplants to intraocular locations usually survive well, partly because of the relative immune privilege provided by the blood-ocular barriers. The choroid, however, is located outside the barriers, and is therefore usually considered not to be immunologically privileged. This study was performed to investigate if transplants could survive in the choroid, and, if so, if they develop some sort of blood transplant barrier. Embryonic retinas from pigmented rabbits at stage E 15 (embryonic day 15) or E 22 were dissected and transplanted into the choroid of 29 adult animals of the same strain. As controls, a similar retinal transplant was placed in the subretinal space in six animals and in the subconjunctival space in another six animals. The animals were killed at intervals up to 8 weeks and the eyes were analysed by light microscopy, immunohistochemistry and morphometry. Some of the animals received Evan's Blue intravenously before termination. Eighty-three per cent of the choroidal transplants survived until termination. All six subretinal but none of the six subconjunctival transplants survived. Both choroidal and subretinal grafts developed rosettes, i.e. rounded formations of retinal cells organized in layers. The different retinal cells developed normal reactivity for the intracellular markers rhodopsin, neurofilament 160 kDa, vimentin and GFAP. Evan's Blue and endogenous serum albumin were used as markers for the patency of the blood-ocular barriers. Evan's Blue was not excluded from the transplants in the early phase up to day 8 after the transplantation. The Evan's Blue content diminished with longer survival times, and after 40 days almost no Evan's Blue was present in the transplants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Adrenoceptor mechanisms in epinephrine-induced anterior choroidal vasoconstriction in cats.

These studies were undertaken to determine the role of epinephrine in the anterior choroidal circulation and to define the relative contribution of adrenoceptor subtypes in this response. Intra-arterial administration of l-epinephrine (0.03-1 microgram) produced vasoconstrictor responses in the anterior choroid of anesthetized cats as measured using laser-Doppler flowmetry. Ipsilateral nictitating membrane contractions were simultaneously recorded. Responses of both organs were blocked by intravenous treatment with the non-selective alpha-adrenoceptor antagonist phentolamine; however, only nictitating membrane contractions were significantly antagonized with the selective alpha 1-adrenoceptor antagonist, prazosin. In contrast, alpha 2-adrenoceptor blockade with rauwolscine had no depressant effect on the nictitating membrane but was a potent antagonist for epinephrine-induced ocular vasoconstriction. This differential ocular receptor type activation was confirmed with the use of more selective alpha-adrenoceptor agonists. Both the alpha 1-adrenoceptor agonist, methoxamine, and the selective alpha 2-adrenoceptor stimulant, B-HT 933, produced choroidal vasoconstriction when given intra-arterially. B-HT 933 was as potent as methoxamine in producing choroidal vasoconstriction which suggests a high ratio of alpha 2-adrenoceptors in this vascular bed. B-HT 933 was much less potent than methoxamine in producing contraction of the nictitating membrane. These results demonstrate the usefulness of laser-Doppler flowmetry in studies of the choroidal circulation and suggest that, unlike the nictitating membrane, epinephrine-induced anterior segment vasoconstriction is mediated by both postjunctional alpha 1- and alpha 2-adrenoceptors with alpha 2-adrenoceptors being predominant.

Adrenergic alpha-Agonists↗
PubMed1996

Study of choroidal blood flow by comparison of SLO fluorescein angiography and microspheres.

Choroidal hemodynamics estimated with parameters describing the dye build-up curves obtained with video fluorescein angiography, were compared with a classical regional blood flow measurement: radioactively labelled microspheres. Video fluorescein angiograms (Rodenstock's SLO 101) and microspheres blood flow measurements were made in 13 anaesthetized pigmented rabbits. Ocular perfusion pressures were varied from 60 to 15 mmHg by changing the intraocular pressure. The angiographically derived dye build-up curves were described by means of an exponential model. One of the model parameters is the time constant tau theoretically reflecting local blood refreshment time. Labelled microspheres act as a non-recirculating blood flow indicator, enabling the estimation of regional blood flows. The relation between choroidal blood flow and perfusion pressure is nearly linear, suggesting the passive nature of choroidal vasculature. There is a significant correlation between tau and microspheres flow (R = 0.67, P < 0.01). According to the rheological model the product of blood flow and tau corresponds to the relevant blood volume. Hence, a function for the volume of the choriocapillaris as a function of perfusion pressure was established. The model parameter tau can be interpreted as the local blood refreshment time. Since the parameter tau, unlike microspheres, can be used clinically, tau may be used to retrieve information on choroidal hemodynamics in clinical practice. Information on the spatial distribution of choroidal hemodynamics is also obtained.

Animals↗
PubMed1999

X-ray microanalysis of melanin granules of retinal pigment epithelium and choroid in hereditary copper deficient mice (macular mice).

The role of trace elements in vivo has not been completely clarified. Trace elements were studied in melanin granules in the retinal pigment epithelium (RPE) and choroid of hereditary copper-deficient macular mice as a model of Menkes' disease. The analysis of elements in these melanin granules was done by new methods: freeze-embedding and an energy dispersive X-ray microanalysis (EDX). We used 14-day- and 1-month-old male hemizygote macular mice for the experiments and normal litter-mates as controls. Melanin granules in RPE and choroid contained sulfur, chloride, calcium, iron, copper and zinc. Calcium and copper were especially abundant in 14-day-old hemizygote macular mice, although there were few melanin granules in their RPE. The fact that copper was most abundant in the melanin granules in the RPE of 14-day-old macular mice suggests that the synthesis of melanin granules in the RPE and choroid of the hemizygote macular mice cannot be completed because of the lower activity of copper-containing enzymes such as tyrosinase and the abnormal copper distribution in various organs. Therefore, the melanin granules in the RPE and choroid of hemizygote macular mice are irregular in shape and few in number. Large amounts of copper concentrated in melanin granules in the RPE and choroid of hemizygote macular mice might induce quantitative abnormalities of trace elements.

Aging↗
PubMed2000

Choroidal retinoic acid synthesis: a possible mediator between refractive error and compensatory eye growth.

Research over the past two decades has shown that the growth of young eyes is guided by vision. If near- or far-sightedness is artificially imposed by spectacle lenses, eyes of primates and chicks compensate by changing their rate of elongation, thereby growing back to the pre-lens optical condition. Little is known about what chemical signals might mediate between visual effects on the retina and alterations of eye growth. We present five findings that point to choroidal retinoic acid possibly being such a mediator. First, the chick choroid can convert retinol into all-trans-retinoic acid at the rate of 11 +/- 3 pmoles mg protein(-1) hr(-1), compared to 1.3 +/- 0.3 for retina/RPE and no conversion for sclera. Second, those visual conditions that cause increased rates of ocular elongation (diffusers or negative lens wear) produce a sharp decrease in all-trans-retinoic acid synthesis to levels barely detectable with our assay. In contrast, visual conditions which result in decreased rates of ocular elongation (recovery from diffusers or positive lens wear) produce a four- to five-fold increase in the formation of all-trans-retinoic acid. Third, the choroidal retinoic acid is found bound to a 28-32 kD protein. Fourth, a large fraction of the choroidal retinoic acid synthesized in culture is found in a nucleus-enriched fraction of sclera. Finally, application of retinoic acid to cultured sclera at physiological concentrations produced an inhibition of proteoglycan production (as assessed by measuring sulfate incorporation) with a EC50 of 8 x 10(-7) M. These results show that the synthesis of choroidal retinoic acid is modulated by those visual manipulations that influence ocular elongation and that this retinoic acid may reach the sclera in concentrations adequate to modulate scleral proteoglycan formation.

Animals↗
PubMed2000

Velocity measurements of normal and sickle red blood cells in the rat retinal and choroidal vasculatures.

The purpose of this study was to develop an in vivo, noninvasive method to assess the velocities of normal and sickle red blood cells (RBCs) in the retinal and choroidal vasculatures of rats. Human and rat RBCs were isolated from whole blood, labeled with fluorescein isothiocyanate (FITC), and administered intravenously to anesthetized rats. A Rodenstock scanning laser ophthalmoscope (SLO) was used to image the FITC-labeled RBCs as an NTSC video signal. Video sequences of RBC transit in the retinal (pigmented rats) and choroidal (albino rats) vessels were captured directly to digital format. Following in vivo angiography, the animals were sacrificed, the eyes enucleated, and retinas prepared by our adenosine diphosphatase vascular labeling technique for viewing by conventional optical microscopy. Although rat and normal human RBCs differ slightly in size, their velocities were similar in the retinal arteries and capillaries (within 4%). Velocities of RBCs from sickle cell patients (sRBCs) were slower by 12 and 9% in arteries and by 38 and 25% in capillaries, compared to rat and normal human RBCs, respectively. Compared to velocities in retinal capillaries, the velocities in choroidal capillaries were much slower for rat RBCs (77%), normal human RBCs (79%), and sRBCs (67%). In contrast to normal human RBCs, sRBCs were often retained transiently in retinal capillaries at preferred sites, but in choroidal capillaries large numbers of cells were retained for extended periods. SLO imaging of FITC-labeled RBCs in rat retina and choroid provided a reliable method for evaluating normal and abnormal hemodynamics.

Anemia, Sickle Cell↗
PubMed1998

Vasopressin gene expression in rat choroid plexus.

Vasopressin (VP) levels in cerebrospinal fluid (CSF) change in response to physiological stimuli and under various pathological conditions. The sources of CSF VP have yet to be clarified, however. In the present study, we provide evidence indicating that VP is synthesized in the choroid plexus, the primary site of CSF formation. All experiments were performed on adult male Sprague-Dawley rats. The presence of VP mRNA in choroid plexus epithelium was demonstrated by in situ hybridization histochemistry using the 35S-labeled riboprobe that was complementary to cDNA fragment of rat VP encoding the C-terminus part of proVP. In situ hybridization findings were confirmed by reverse transcriptase-polymerase chain reaction analysis. Immunohistochemistry for VP-associated neurophysin (VP-NP), a polypeptide component of proVP, revealed subapical accumulation of VP-NP-immunopositive product in choroidal epithelial cells. Immunoprecipitation and immunoblotting of choroidal protein extracts with anti-VP-NP antibody demonstrated the presence of a approximately 10-kD polypeptide that was also detected in hypothalamus. We hypothesize that the choroid plexus-derived VP exerts autocrine and/or paracrine effects on tissues near the CSF system.

Animals↗
PubMed1995

Retinal and choroidal responses to panretinal photocoagulation: an ultrastructural perspective.

BACKGROUND: There have been few histological or ultrastructural studies of the outer retina and choriocapillaris following panretinal photocoagulation therapy. This investigation examines the long-term morphological effects of panretinal photocoagulation in two patients with type II diabetes who had received laser treatment more than 6 months prior to death. METHODS: Regions of retina and choroid from each patient were fixed in 2.5% glutaraldehyde, dissected out and examined using light microscopy and scanning and transmission electron microscopy. RESULTS: After removing the neural retina, scanning electron microscopy of non-photocoagulated areas of the eye cups revealed normal cobblestone-like retinal pigment epithelial (RPE) cells. Regions with laser scars showed little RPE infiltration into the scar area, although large rounded cells often appeared in isolation within these areas. Sections of the retina and choroid in burn regions showed a complete absence of the outer nuclear layer and photoreceptor cells, with the inner retinal layers lying in close apposition to Bruch's membrane. Non-photocoagulated regions of the retina and choroid appeared normal in terms of both cell number and cell distribution. The RPE layer was absent within burn scars but many RPE-like cells appeared markedly hypertrophic at the edges of these regions. Bruch's membrane always remained intact, although the underlying choriocapillaris was clearly disrupted at the point of photocoagulation burns, appearing largely fibrosed and non-perfused. Occasional choroidal capillaries occurring in this region were typically small in profile and had plump non-fenestrated endothelium. CONCLUSIONS: This study outlines retinal and choroidal cell responses to panretinal photocoagulation in diabetic patients and demonstrates an apparent reduction in the capacity of these tissues to repair laser damage.

Aged↗
PubMed1982

Autonomic innervation of the ocular choroid membrane in the chicken: a fluorescence-histochemical and electron-microscopic study.

The distribution pattern of adrenergic fibres innervating the ocular choroid membrane of the chicken was studied by means of fluorescence and electron microscopy. In addition, the origin of these fibres was investigated after superior cervical ganglionectomy. Adrenergic axons reach the choroid, partly forming the perivascular plexuses and partly running in the choroid nerves and the choroidal branches of the ciliary nerves. The axon terminals distribute to the smooth muscle cells of the arterial wall and to the extensive system of smooth muscle cells of the intervascular stroma. After unilateral ganglionectomy, fluorescent fibres almost completely disappeared, and degenerative changes could be observed in the terminal varicosities on both smooth muscle cell populations. These findings suggest that the adrenergic axons either originate from neurones within the ipsilateral superior cervical ganglion, or pass through this ganglion. The persistence of normal terminals in short- and long-term ganglionectomised animals shows that the vasal and intervascular muscle cells of the choroid membrane are provided with both an adrenergic and a cholinergic innervation.

Adrenergic Fibers↗
PubMed1986

Arginine vasopressin causes morphological changes suggestive of fluid transport in rat choroid plexus epithelium.

The experiments described herein use an in vitro preparation of choroid plexus to demonstrate that it is a vasopressin-responsive organ by morphologic criteria. Choroid plexus from rats was incubated for one hour in graded concentrations of arginine vasopressin (AVP). Within physiologic range of molar concentration, incubation in vasopressin induced a decrease in basal and lateral spaces in choroid plexus epithelial cells as well as an increase in number of dark cells. The number of cells with basal spaces decreased significantly from 82.7 +/- 9.2 in control tissue to 19 +/- 18 in tissue incubated in 10(-12) M AVP; similarly, the number with lateral cellular spaces decreased from 20 +/- 8.8 to 7.6 +/- 2.2 cells in 10(-10) M AVP. Dark cells increased in number from 3.8 +/- 2.6 in control conditions to 49 +/- 4 with 10(-9) M vasopressin. These data suggest important effects of arginine vasopressin in cerebrospinal fluid (CSF) on choroid plexus, compatible with enhanced fluid transport across choroid epithelial cells.

Animals↗
PubMed1992

Retrograde filling of the anterior choroidal artery: vertebral angiographic sign of obstruction in the carotid system.

Retrograde filling of seven anterior choroidal arteries from the posterior circulation was observed on a vertebral angiogram in six patients with occlusion of the proximal anterior choroidal artery or of the internal carotid artery. In one patient with thrombotic occlusion of the internal carotid artery, the enlarged anterior choroidal artery functioned as a major collateral pathway from the posterior circulation to the territory of the middle cerebral artery. Retrograde filling of the anterior choroidal artery is a sign of obstruction changes in the ipsilateral carotid artery at or proximal to the origin of the anterior choroidal artery.

Adolescent↗
PubMed1981

Focal ependymal differentiation in choroid plexus papillomas. An immunoperoxidase study.

Choroid plexus papillomas are usually easily distinguishable from papillary ependymomas by their delicate fibrovascular stroma and their cytologic similarity to normal choroid plexus epithelium. Exceptionally, however, examples are met which give rise to diagnostic difficulty. We therefore tested 22 choroid plexus papillomas for the presence of glial fibrillary acidic (GFA) protein using the immunoperoxidase technique. Positivity for the protein was found focally in epithelial tumor cells in nine of the 22 papillomas. All were in adults ranging from 19-66 years of age. Eight of the nine tumors originated in the 4th ventricle or one of its lateral recesses. In six papillomas showing GFA protein in the cells, intracellular fibrils were found in a small number of elongated epithelial cells with the PTAH and/or Masson trichrome stains; in all these six cases, the GFA protein-positive cells were considerably more numerous than cells containing fibrils. Normal choroid plexus epithelium lacks GFA protein, but pathologically altered ependymal cells are often GFA protein-positive. Our findings therefore suggest that focal divergent glial (presumably ependymal) differentiation may be expressed in neoplastic choroid plexus epithelium, consistent with the origin of this epithelium from primitive neuroepithelial (ventricular) cells.

Adolescent↗
PubMed1995

Morphological modifications of the choroid plexus in a rodent model of acute ventriculitis induced by gram-negative liquoral sepsis. Possible implications in the pathophysiology of hypersecretory hydrocephalus.

Gram-negative bacterial infections of the central nervous system are generally associated with high morbidity and mortality rates. In patients with ventriculitis induced by gram-negative liquoral sepsis, a reduction in cerebrospinal fluid formation has been reported, suggesting that gram-negative ventriculitis is able per se to alter the normal functioning of the choroid plexus. The aim of the present study was to analyse, for the first time in the rat, the effects of acute ventriculitis on the ultrastructure of the choroid plexus. A simple and inexpensive experimental model of acute ventriculitis was developed: we injected into the cisterna magna of rats 10(3) CFU of live Escherichia coli, inducing septic ventriculitis without major neurological deficits. Histological examinations of rodent choroid plexus 24 h after the injection revealed patches of altered epithelium, with swollen and vacuolated ependymal cells associated with leukocyte infiltration. Electron microscopy demonstrated a reduced number of microvilli and flattening of the epithelial surface. These results (a) indicate that gram-negative septic ventriculitis is able to induce visible ultrastructural alterations of the choroid plexus which (b) are consistent with a picture of marked reduction of the functioning epithelial choroid plexus surface, and (c) highlight the potential usefulness of our rodent acute ventriculitis model for developing treatment modalities.

Acute Disease↗
PubMed1992

Unusual MRI findings in metastatic carcinoma to the choroid and optic nerve: a case report.

A 51 year old man with biopsy proven pulmonary sarcoidosis and skin test positive for tuberculosis presented with features of an amelanotic flat choroidal mass suggestive of choroiditis. The mass enlarged despite corticosteroids and anti-tuberculous medications. A thorough systemic evaluation for possible primary tumor metastatic to the choroid was negative. Further clinical evaluation and magnetic resonance imaging suggested a diffuse primary choroidal malignant melanoma with optic nerve invasion. The eye was enucleated and the mass proved histopathologically to be a mucin secreting adenocarcinoma of unknown origin despite a repeat systemic work-up. The patient died three months after the onset of symptoms and three weeks after enucleation with diffuse metastases from an unknown primary cancer. Magnetic resonance imaging (MRI) is usually helpful in the differentiation of uveal melanoma from uveal metastasis. In this case, however, it suggested the diagnosis of a diffuse choroidal melanoma. The reason for the atypical MRI findings will be discussed.

Adenocarcinoma↗
PubMed1997

Visualization of retinal and choroidal blood flow with fluorescein leukocyte angiography in rabbits.

PURPOSE: To visualize the retinal and choroidal leukocytes in rabbits with a new technique, fluorescein leukocyte angiography using a scanning laser ophthalmoscope. METHODS: Blood was withdrawn from an ear vein of a rabbit (New Zealand White), mixed with fluorescein dye in a test tube and centrifuged. The yellow-brown coat layer containing fluorescein-stained leukocytes was collected and injected into the ear vein of the same rabbit while performing fluorescein angiography with a scanning laser ophthalmoscope. The angiographic image displaying circulating fluorescent leukocytes in retinal and choroidal vessels was recorded on a videotape. RESULTS: Fluorescent leukocytes were clearly visible in the retinal arteries, capillaries, veins and choroidal vessels for more than 1 h. Plugging of leukocytes was seen throughout this period of time in choroidal vessels, while plugging was rare in retinal vessels. CONCLUSIONS: Fluorescein leukocyte angiography is a new technique which can be used for visualization of the leukocytes in retinal and choroidal vessels non-invasively and in vivo.

Animals↗