Ketamine, a widely used anesthetic in a variety of species, has been shown to exert a potential teratogenic effect during the early life stages of zebrafish. A number of mechanisms have been suggested for the etiology of teratogens. One of the most studied involves reactive oxygen species (ROS) formation and oxidative damage. In this study, zebrafish embryos were used to analyze oxidative stress as a potential mechanism of ketamine-induced toxicity. The changes in the accumulation and in vivo patterns of ROS, enzymatic activities (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE)), glutathione levels (oxidized (GSSG) and reduced (GSH)), oxidative damage (lipid peroxidation (LPO) and protein carbonyls (CO)) and gene expression (gclc, gstp1, sod1 and cat) were evaluated at 8 and 24 hours post fertilization (hpf) in zebrafish embryos exposed during 20 minutes to 0.2, 0.4 and 0.8 mg mL⁻¹ ketamine in the course of blastula (2.5 hours post fertilization-hpf), gastrula (5.5 hpf) and segmentation (10.5 hpf). Although no changes in ROS patterns were visible after all ketamine exposures, an increase in GSH levels was observed after exposure during blastula, indicating possible alterations in cell oxidative capacity. After exposure in gastrula, an increase in SOD and CAT enzymatic activities along with an increase in GSSG levels were observed at 8 hpf. At 24 hpf, CAT activity remained higher in ketamine exposed groups. The expression of the cat gene was also augmented at this time point. The changes were related with the ability of the embryo to handle oxidative stress and to a turning point during development of the oxidative defense system. At segmentation, the exposure to ketamine induced changes in the accumulation of ROS and sod gene expression which were related to protective mechanisms against ketamine-induced oxidative stress. Changes in acetylcholinesterase were also observed which may be related to changes in ROS. The overall results show that ketamine induces phase-dependent oxidative stress misregulation that could be the key factor for ketamine toxicity and could help to elucidate and provide more information on the mechanism of embryotoxicity of ketamine.

Heavy metals in urban soils may impose a threat to public health and may negatively affect urban tree viability. Vegetation spectroscopy techniques applied to bio-indicators bring new opportunities to characterize heavy metal contamination, without being constrained by laborious soil sampling and lab-based sample processing. Here we used Tilia tomentosa trees, sampled across three European cities, as bio-indicators i) to investigate the impacts of elevated concentrations of cadmium (Cd) and lead (Pb) on leaf mass per area (LMA), total chlorophyll content (Chl), chlorophyll a to b ratio (Chla:Chlb) and the maximal PSII photochemical efficiency (Fv/Fm); and ii) to evaluate the feasibility of detecting Cd and Pb contamination using leaf reflectance spectra. For the latter, we used a partial-least-squares discriminant analysis (PLS-DA) to train spectral-based models for the classification of Cd and/or Pb contamination. We show that elevated soil Pb concentrations induced a significant decrease in the LMA and Chla:Chlb, with no decrease in Chl. We did not observe pronounced reductions of Fv/Fm due to Cd and Pb contamination. Elevated Cd and Pb concentrations induced contrasting spectral changes in the red-edge (690-740 nm) region, which might be associated with the proportional changes in leaf pigments. PLS-DA models allowed for the classifications of Cd and Pb contamination, with a classification accuracy of 86% (Kappa = 0.48) and 83% (Kappa = 0.66), respectively. PLS-DA models also allowed for the detection of a collective elevation of soil Cd and Pb, with an accuracy of 66% (Kappa = 0.49). This study demonstrates the potential of using reflectance spectroscopy for biomonitoring of heavy metal contamination in urban soils.