Nonlinear optical waveguides generated in lithium niobate by swift-ion irradiation at ultralow fluences

A novel method to produce optical waveguides is demonstrated for lithium niobate (LiNbO(3)). It is based on electronic excitation damage by swift ions, i.e., with energies at approximately 1 MeV/amu or above. The new technique uses high-energy medium-mass ions, such as Cl, with electronic stopping powers above the threshold value for amorphization (5-6 keV/nm), reaching the maximum value a few micrometers inside the crystal. At the ultralow fluence regime (10(12)-10(13) cm(-2)) an effective nanostructured medium is obtained that behaves as an optical waveguide where light propagates transversally to the amorphous nanotracks created by every single impact. The method implies a reduction of 4 orders of magnitude with respect to He implantation. The optical waveguides present reasonable losses (~10 dB/cm) and significant second-harmonic generation (SHG) and electro-optic (EO) responses (>50% bulk) for the lowest fluences.

Early postoperative response of cytokines in liver transplant recipients

We evaluated the early postoperative response of several cytokines (IL-2, IL-4, IL-6, IL-10, TNF-alpha, IFN-gamma) prior to liver transplantation (T(0)) as well as 1, 6, and 12 hours and 1, 2, 3, 5, and 7 days afterward. Cytokine concentrations were correlated with serum levels of bilirubin as a predictor of postoperative complications. Cytokine levels were determined in plasma samples from 16 liver transplant recipients (13 men, 3 women) aged 43 to 61 years. IL-6 and IL-10 reached their maximum concentrations 1 hour after transplantation. Each increase in IL-6 correlated to a rise in IL-10. IL-2, IL-4, TNF-alpha, and IFN-gamma had a particular time-course for each patient studied. Bilirubin fell to almost normal values but not in cases of postoperative complications, where IL-6 showed values four times higher compared to those of liver transplant recipients who did not show postoperative complications. IL-6 and IL-10 plasma concentrations and serum bilirubin level might be useful as a predictive factor of postoperative complications in liver transplant recipients.

Time course of antioxidant enzyme activities in liver transplant recipients

Reactive oxygen species (ROS) play a central role in ischemia-reperfusion injury after organ transplantation. They are degraded by endogenous radical scavengers such as antioxidant enzymes. The purpose of this study was to evaluate the temporal variations of antioxidant enzyme activities in liver transplant recipients. The study was performed in 13 liver transplant patients (11 men and 2 women). Blood samples were obtained pre- and postsurgical intervention: before transplant (T(0)), and 1, 6, 12, 24, 48, and 72 hours, as well as 5 and 7 days thereafter. We determined total and specific superoxide dismutase (SOD) activity, catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) activities as well as malondialdehyde (MDA) and low-density lipoproteins (LDL). The results showed increased SOD and mainly GPX activities after liver transplantation, which correlated with MDA levels. Total SOD activity was mainly represented by Mn-SOD (75%) and Cu,Zn-SOD (25%), whereas Fe-SOD was not detected. In conclusion, the enhanced antioxidant enzyme activities reported in this study indicated a control of oxidative stress generated in liver transplantation. In this sense, although MDA levels showed an enormeous increase at 1 hour after transplantation, the lipid peroxidation was compensated for by GPX activity.