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Abstract Purpose  To check differences in visual function between Wistar (albino) and Long-Evans (pigmented) rats. Methods  The animals were born in our facilities and reared under identical light conditions avoiding bright light. Visual electrophysiology was performed at the ages of 1.5, 4, 7 and 10 months (electroretinography, ERG) and at 1.5 and 7 months (visual evoked potentials, VEP). Results  ERG measurements showed that: 1) The amplitudes of both scotopic and photopic b-waves were markedly larger in Long-Evans rats than in Wistar rats, and also the amplitudes of scotopic oscillatory potentials and photopic 30 Hz Flicker amplitudes, 2) scotopic a-wave amplitudes were larger in Wistar rats at low light intensities, whereas they were smaller in bright light, 3) both a-wave and b-wave latencies were shorter in Wistar rats, 4) the maximum response RmP3 was larger in Long-Evans rats, 5) the sensitivity parameter S was larger in Wistar rats, and 6) the post-receptoral response of cones was smaller in Wistar rats. In the VEP measurements, amplitudes of both photopic and scotopic visual evoked potentials of Long-Evans rats were only slightly larger than those of Wistar rats. Conclusions  ERG b-wave amplitudes are markedly decreased in Wistar rats, which requires further investigation. As the b/a and OP/a ratios were also decreased in Wistar rats, it can be suggested that post-receptoral processing, in particular, is impaired in albino animals. [ABSTRACT FROM AUTHOR]

Abstract Aim  To compare the antiproliferative and cytotoxic properties of bevacizumab (Avastin), pegaptanib (Macugen) and ranibizumab (Lucentis) on human retinal pigment epithelium (ARPE19) cells, rat retinal ganglion cells (RGC5) and pig choroidal endothelial cells (CEC). Methods  Monolayer cultures of ARPE19, RGC5 and CEC were used. Bevacizumab (0.1–0.3 mg/ml), pegaptanib (0.025–0.08 mg/ml) or ranibizumab (0.04–0.125 mg/ml) diluted in culture medium were added to the cells. Expression of VEGF-receptors (VEGFR1 and VEGFR2) and von Willebrand factor (a marker for endothelial cells) were analysed by immunohistochemistry. CEC cells were stimulated with VEGF. Cellular proliferative activity was monitored by BrdU-incorporation into cellular DNA. For cytotoxicity assays cells were grown to confluence and then cultured in a serum-depleted medium to ensure a static milieu. MTT-test was performed after one day. Results  CEC and ARPE19 cells stained positively for VEGFR1 and VEGFR2. More than 95% of the CEC cells were positive for von Willebrand factor. Ranibizumab reduced CEC cell proliferation by 44.1%, bevacizumab by 38.2% and pegaptanib by 35.1% when the drugs were used at their established clinical doses. The differences, however, between the three drugs in respect to cell growth inhibition were not statistically significant. Only a mild antiproliferative effect of bevacizumab or pegaptanib on ARPE19 cells could be observed. Ranibizumab did not alter ARPE19 cell proliferation. No cytotoxicity on RGC5, CEC and ARPE19 cells could be seen. Conclusions  Bevacizumab, pegaptanib and ranibizumab significantly suppress choroidal endothelial cell proliferation. However, when used at the currently established doses none of the drugs was superior over the others in respect to endothelial cell growth inhibition. The biocompatibility of all three drugs — including the off-label bevacizumab — seems to be excellent when used at the currently recommended intravitreal dose. [ABSTRACT FROM AUTHOR]

Abstract Background  Tyrosinase (EC 1.14.18.1) is the key enzyme of melanin pigment formation and it is unclear whether it is synthesized in human postnatal retinal pigment epithelium (RPE). In this study, we investigated if phagocytosis of rod outer segments (ROS) can increase tyrosinase expression in vitro. Methods  Primary cultures of human RPE cells were fed with isolated ROS from cattle and with latex particles. After phagocytosis, RPE cells were tested for tyrosinase presence and activity with several independent methods: (1) immunocytochemistry with anti-tyrosinase antibodies and (2) ultrastructural as well as light microscopic DOPA histochemistry; (3) mRNA was isolated from human RPE before incubation with ROS and 5, 20 and 40 h after feeding with ROS. The amount of tyrosinase mRNA was determined quantitatively by real-time reverse transcription polymerase chain reaction (RT-PCR), and the tyrosinase activity was investigated by measuring tyrosine hydroxylase activity using [3H]tyrosine. Results  Tyrosinase was found in fed RPE cells using these methods, but was absent without feeding. Furthermore, we showed co-localization of rhodopsin and tyrosinase in the fed RPE cells. Contrary to tyrosinase activity, the mRNA for tyrosinase was clearly present in the cultured RPE cells which had not been exposed to ROS, decreased significantly from 5 h after exposure to ROS and returned to its original non-fed level 40 h after ROS feeding. Conclusion  Our study does not present new evidence that de novo melanogenesis takes place in the adult differentiated RPE. However, in contrast to the classic hypothesis, which states that tyrosinase is only detected in embryos, we provide evidence with several independent methods that the expression of tyrosinase and its enzymatic activity are induced in cultured human adult RPE by phagocytosis of ROS. [ABSTRACT FROM AUTHOR]