Transcorneal Electrical Stimulation Shows Neuroprotective Effects in Retinas of Light-Exposed Rats

PURPOSE. To examine the effects of transcorneal electrical stimulation (TES) on retinal degeneration of light-exposed rats. METHODS. Thirty-three Sprague Dawley albino rats were divided into three groups: STIM (n = 15) received 60 minutes of TES, whereas SHAM (n = 15) received identical sham stimulation 2 hours before exposure to bright light with 16,000 lux; healthy animals (n = 3) served as controls for histology. At baseline and weekly for 3 consecutive weeks, dark-and light-adapted electroretinography was used to assess retinal function. Analysis of the response versus luminance function retrieved the parameters Vmax (saturation amplitude) and k (luminance to reach 1/2Vmax). Retinal morphology was assessed by histology (hematoxylin-eosin [HE] staining; TUNEL assay) and immunohistochemistry (rhodopsin staining). RESULTS. Vmax was higher in the STIM group compared with SHAM 1 week after light damage (mean intra-individual difference between groups 116.06 mu V; P = 0.046). The b-wave implicit time for the rod response (0.01 cd.s/m(2)) was lower in the STIM group compared with the SHAM group 2 weeks after light damage (mean intra-individual difference between groups 5.78 ms; P = 0.023); no other significant differences were found. Histological analyses showed photoreceptor cell death (TUNEL and HE) in SHAM, most pronounced in the superior hemiretina. STIM showed complete outer nuclear layer thickness preservation, reduced photoreceptor cell death, and preserved outer segment length compared with SHAM (HE and rhodopsin). CONCLUSIONS. This sham-controlled study shows that TES can protect retinal cells against mild light-induced degeneration in Sprague Dawley rats. These findings could help to establish TES as a treatment in human forms of retinal degenerative disease. (Invest Ophthalmol Vis Sci. 2012;53:5552-5561) DOI: 10.1167/iovs.12-10037

Deleterious Effect of Hypothermia in Myocardial Protection Against Cold Ischemia: A Comparative Study in Isolated Rat Hearts

Background. There is a growing need to improve heart preservation benefit the performance of cardiac operations, decrease morbidity, and more important, increase the donor pool. Therefore, the objective of this study was to evaluate the cardioprotective effects of Krebs-Henseleit buffer (KHB), Bretschneider-HTK (HTK), St. Thomas No. 1 (STH-1), and Celsior (CEL) solutions infused at 10 degrees C and 20 degrees C. Methods. Hearts isolated from male albino Wistar rats and prepared according to Langendorff were randomly divided equally into 8 groups according to the temperature of infusion (10 degrees C or 20 degrees C) and cardioprotective solutions (KHB, HTK, STH-1, and CEL). After stabilization with KHB at 37 degrees C, baseline values were collected (control) for heart rate (HR), left ventricle systolic pressure (LVSP), coronary flow (CF), maximum rate of rise of left ventricular pressure during ventricular contraction (+dP/dt) and maximum rate of fall of left ventricular pressure during left ventricular relaxation (-dP/dt). The hearts were then perfused with cardioprotective solutions for 5 minutes and kept for 2 hours in static ischemia at 20 degrees C. Data evaluation used analysis of variance (ANOVA) in all together randomized 2-way ANOVA and Tukey's test for multiple comparisons. The level of significance chosen was P < .05. Results. We observed that all 4 solutions were able to recover HR, independent of temperature. Interestingly, STH-1 solution at 20 degrees C showed HR above baseline throughout the experiment. An evaluation of the corresponding hemodynamic values (LVSP, +dP/dt, and -dP/dt) indicated that treatment with CEL solution was superior at both temperatures compared with the other solutions, and had better performance at 20 degrees C. When analyzing performance on CF maintenance, we observed that it was temperature dependent. However, when applying both HTK and CEL, at 10 degrees C and 20 degrees C respectively, indicated better protection against development of tissue edema. Multiple comparisons between treatments and hemodynamic variable outcomes showed that using CEL solution resulted in significant improvement compared with the other solutions at both temperatures. Conclusion. The solutions investigated were not able to fully suppress the deleterious effects of ischemia and reperfusion of the heart. However, these results allow us to conclude that temperature and the cardioprotective solution are interdependent as far as myocardial protection. Although CEL solution is the best for in myocardial protection, more studies are needed to understand the interaction between temperature and perfusion solution used. This will lead to development of better and more efficient cardioprotective methods.