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- Engqvist, Cecilia, et al.
(author)
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Interactions between single latex particles and silica surfaces studied with AFM
- 2007
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In: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 302:03-jan, s. 197-203
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Journal article (peer-reviewed)abstract
- The spreading of single styrene-acrylic latex particles on silicon oxide C surfaces was studied using atomic force microscopy (AFM). Three latexes with different glass transition temperature (Tg) were used and the effects of temperature, time and preparation method were investigated. Particle sizes and shape were measured with AFM and the contact angles were calculated. The observed rate for the spreading of latex particles was low and it took several days before the particles reached steady state, even at temperatures well above their T-g. The experimental particle spreading results deviated with two orders of magnitude from predictions Using the WLF equation for polymer diffusion. The deviation could be attributed to polymer-surface interactions that slowed down the particle spreading. The work of adhesion was calculated using two models. The results from using the regular Young-Dupre equation and a modified version of this equation that also included the mechanical properties (E-modulus and Poisson's ratio) of the latexes, were compared. For soft latex particles the results from the two models agreed well and were of the order of 75 J/m(2), but for glassy latexes the Young-Dupre equation underestimated the work of adhesion.
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- Morén, Håkan, et al.
(author)
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Angiography and mfERG show that blood supply to the pig retina may be both ipsilateral and contralateral.
- 2013
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In: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 54:9, s. 6112-6117
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Journal article (peer-reviewed)abstract
- Purpose: We recently presented a transfemoral endovascular coiling technique for inducing experimental retinal ischemia in pigs. Substantial variation was seen in the degree of ischemia. It was hypothesized that the blood supply to the retina may originate from both the ipsi- and contralateral ophthalmic arteries, and that there may be an interconnecting artery between the eyes. Methods: The external carotid system of ten pigs was catheterized using a fluoroscopy- monitored, transfemoral, endovascular approach. Vascular occlusion was achieved in the ophthalmic artery using coils. The effect of occlusion was examined using angiography and multifocal electroretinography (mfERG). Results: During angiography of the ophthalmic artery on one side, contrast filling was seen in the retinas on both sides, suggesting that the ophthalmic artery on one side may supply both retinas. A blood vessel connecting the eyes was visualized. mfERG recordings showed that the use of coiling to occlude the ophthalmic artery had greater ischemic effects in eyes that depended mainly on the ipsilateral ophthalmic artery for blood supply and smaller ischemic effect in retinas that received blood from both the ipsilateral and contralateral ophthalmic artery via the interconnecting vessel. Conclusions: The blood supply to the retina may originate from both the ipsi- and contralateral ophthalmic artery in the pig. There is an interindividual variability in the ischemic effect of occlusion depending on the architecture of the vasculature. These findings may be important in the development of new animal models of experimental retinal ischemia, since arterial occlusion in one eye may affect the blood supply to the contralateral eye.
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- Morén, Håkan, et al.
(author)
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Endovascular Coiling of the Ophthalmic Artery in Pigs to Induce Retinal Ischemia
- 2011
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In: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 52:7, s. 4880-4885
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Journal article (peer-reviewed)abstract
- PURPOSE. The authors recently showed that the retinal circulation can be accessed by transfemoral endovascular catheterization. The purpose of this study was to examine whether endovascular coiling can be used to induce different degrees of ischemic injury. The possibility of creating occlusions at different sites in the vasculature to cause retinal ischemia with different degrees of severity was investigated. METHODS. The ophthalmic artery was catheterized through the external carotid system using a fluoroscopy-monitored, transfemoral, endovascular approach in 12 pigs (mean weight, 70 kg). The effects were evaluated using angiography and multifocal electroretinography. RESULTS. Occlusion of arteries supplying the retina was established using endovascular coiling. Coiling in the proximal part of the ophthalmic artery caused no or little ischemia, presumably because of collateral blood supply. Coiling in the distal part of the ophthalmic artery, over the branching of the main ciliary artery, caused more severe retinal ischemia. Multifocal electroretinography recordings, which reflect retinal function in an area close to the visual streak, showed decreased amplitudes and increased implicit times after distal occlusion, but not after proximal occlusion of the ophthalmic artery. The responses were similar 1 hour and 72 hours after coiling, indicating that a permanent ischemic injury was established. CONCLUSIONS. The porcine ophthalmic artery can be occluded using an endovascular coiling technique. This provides an experimental animal model of retinal ischemia in which occlusion at different sites of the vasculature produces different degrees of severity of the ischemic damage. (Invest Ophthalmol Vis Sci. 2011;52:4880-4885) DOI:10.1167/iovs.11-7628
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- Morén, Håkan, et al.
(author)
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Multifocal electroretinogram for functional evaluation of retinal injury following ischemia-reperfusion in pigs.
- 2010
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In: Graefe's Archive for Clinical and Experimental Ophthalmology. - : Springer Science and Business Media LLC. - 1435-702X .- 0721-832X. ; 248, s. 627-634
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Journal article (peer-reviewed)abstract
- BACKGROUND: Multifocal electroretinogram (mfERG) has the power to discriminate between localized functional losses and overall retinal changes when evaluating retinal injury. So far, full-field ERG has been the gold standard for examining retinal ischemia and the effects of different neuroprotectants in experimental conditions. The aim of the present study was to establish mfERG, with simultaneous fundus monitoring, for analyzing the localized functional response in the retina after ischemia-reperfusion in the porcine eye. METHODS: 70 kg pigs underwent pressure-induced retinal ischemia (1 hour) followed by reperfusion. mfERG recordings were obtained before and after ischemia, followed by 1 and 5 hours of reperfusion. Individual components of the summed mfERG responses were correlated to ischemia and the time of reperfusion. RESULTS: The visual streak area had significantly higher amplitudes than the optic nerve head and the area in between, suggesting that the mfERG monitors localized functional retinal responses. The mfERG recordings were altered following ischemia-reperfusion. In one group of animals, there was a complete flattening of the mfERG waveforms, indicating complete ischemic injury. In the other group of animals, ischemia-reperfusion altered the mfERG such that the implicit time was increased (20.82 +/- 0.18 before ischemia and 21.57 +/- 0.21 after ischemia and 1 hour of reperfusion, in the visual streak area, p < 0.05) and the amplitude was decreased (13.16 +/- 2.3 before ischemia and 11.47 +/- 0.88 after ischemia and 1 hour of reperfusion, in the visual streak area, p < 0.001), suggesting partial ischemic injury. CONCLUSIONS: In conclusion, the porcine model of pressure-induced retinal ischemia-reperfusion results in mfERG changes, typical for retinal ischemia. mfERG may be a useful tool for evaluating and monitoring localized cone dysfunction after an ischemic injury.
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| 7. |
- Morén, Håkan, et al.
(author)
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The porcine retinal vasculature can be accessed using an endovascular approach, a new experimental model for retinal ischemia.
- 2009
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In: Investigative Ophthalmology & Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 1552-5783. ; 50:11, s. 5504-5510
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Journal article (peer-reviewed)abstract
- Purpose. The aim was to examine if the retinal circulation in the pig can be accessed using interventional neuroradiology and to explore the possibility to create occlusions that result in experimental retinal ischemia. Methods. Six experiments were performed using 100 kg pigs. The external carotid system was catheterizised using fluoroscopy monitored, transfemoral, endovascular approach. Transient and permanent vascular occlusions were performed using an angioplasty balloon catheter or a liquid embolic agent that was administered via an injection-catheter. Results. A technique for transfemoral catheterization of arteries supplying the retina was established. The ophthalmic artery was demonstrated to give rise to the main ciliary artery, from which the retinal artery branched as a single or several arteries. A balloon-catheter could be introduced into the ophthalmic artery, but not into the main ciliary artery. An injection-catheter could, in all experiments, be introduced into the main ciliary artery and, in some experiments, into the retinal artery. Occlusion of the ophthalmic artery, over the branching of the main ciliary artery, caused incomplete ischemia, presumably due to collaterals feeding the distal parts of the vasculature. mfERG recordings showed decreased amplitudes and increased implicit times, indicating retinal ischemia. Occlusion of the ciliary and retinal arteries caused complete ischemia, as shown by complete flattening of the mfERG recordings and, by indirect ophthalmoscopy, blanching of the retinal arteries and a pale retina Conclusions. We prove for the first time that the ophthalmic and retinal artery can be catheterizised using a transfemoral endovascular approach. This technique may be useful to produce clear-cut experimental retinal ischemia.
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