Extending bioelectric navigation for displacement and direction detection.

PURPOSE: Bioelectric navigation is a navigation modality for minimally invasive endovascular procedures promising non-fluoroscopic navigation. However, the method offers only limited navigation accuracy between anatomical features and expects the tracked catheter to move only in one direction at all times. We propose to extend bioelectric navigation with additional sensing capabilities, allowing for the estimation of the distance traveled by the catheter, thereby improving accuracy between feature locations and allowing to track also under alternating forward- and backward motion. METHODS: We perform experiments in finite element method (FEM) simulations and in a 3D printed phantom. A solution for estimating the traveled distance using a stationary electrode is proposed, together with an approach on how to evaluate the signals obtained with this additional electrode. We investigate the effects of surrounding tissue conductance on this approach. Finally, the approach is refined in order to mitigate the effects of parallel conductance on the navigation accuracy. RESULTS: The approach allows to estimate the catheter movement direction and the distance traveled. Simulations show absolute errors below 0.89 mm for non-conducting surrounding tissue, but errors up to 60.27 mm when the tissue is electrically conductive. This effect can be mitigated by a more sophisticated modeling (errors up to 33.96 mm). In experiments in a 3D printed phantom, the mean absolute error over 6 catheter paths is 6.3 mm, with standard deviations smaller than or equal to 1.1 mm. CONCLUSIONS: Extending the setup of bioelectric navigation with an additional stationary electrode allows to estimate the distance traveled by the catheter, as well as the movement direction. The effects of parallel conductive tissue could be partially mitigated in simulations, but further research is needed to investigate these effects in real biological tissue, and to bring the introduced errors down to a clinically acceptable level.

Phytoremediation of organic xenobiotics - Glutathione dependent detoxification in Phragmites plants from European treatment sites.

Studies on the uptake of several organic xenobiotics and on their subsequent conjugation to biomolecules have been performed to elucidate the use of reed plants in phytoremediation of polluted water. Phragmites australis plants were able to accumulate organic xenobiotics in their rhizomes. The uptake was correlated to the logKOW and pKa of the xenobiotics and highest with compounds exhibiting logKOWs between 1 and 3. Detoxification of xenobiotics was demonstrated when the activity of glutathione S-transferase was determined in plants from various treatment sites. Enzyme activities were strongly dependent on the provenience of the plant and the history of the stand. Detoxification enzymes were also inducible. Naphthylic acetic acid (NAA), 2,4-dichlorophenol and BION were tested as potential inducers. BION was able to induce the GST activity 5-fold, albeit only for a short period of hours. The mechanism of induction and the flexibility of the detoxification system of certain ecotypes of reed toward stress or the pollution level will require further investigation.

Detoxification of herbicides in Phragmites australis.

Unintentional loss of herbicides into drainage ditches, shores or other waterbodies may cause large problems in farmland. Therefore strategies for the phytoremediation of agrochemicals and especially herbicides have become a topic of great interest in many agricultural areas. However, in order to establish effective biological pollution control, information on the detoxification capacity of riparian plants and aquatic macrophytes (e.g., Phragmites australis) is important to build up effective buffer stripes. We determined the detoxification capacity of Phragmites australis roots and leaves for the conjugation of agrochemicals to glutathione by assaying the model substrate CDNB as well as the herbicides fenoxaprop-P, propachlor, pethoxamid and terbuthylazine. Specific GST activities were always higher in the rhizomes (6.78 +/- 0.88 microkat/mg protein for CDNB) than in leaves (1.08 +/- 0.21 microkat/mg protein). The detoxification capacity is distributed across an array of GST isoforms. In summary, Phragmites australis seems to be efficient in herbicide detoxification and a good candidate for phytoremediation of effluents from agricultural sites.