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Mitochondrial Mechanisms of Tubular Injury
Published in Robin S. Goldstein, Mechanisms of Injury in Renal Disease and Toxicity, 2020
Rick G. Schnellmann, Richard D. Griner
S-(1,1,2,2,-Tetrafluoroethyl)-l-cysteine (TFEC; Figure 4) is a metabolite of tetrafluoroethylene and exhibits toxicological sequelae which include impairment of respiration (Groves et al., 1993) and inhibition of GSH reductase and dihydrolipoyl dehydrogenase (Lock and Schnellmann, 1990). TFEC inhibited respiration in isolated mitochondria in the presence of site I and site II substrates (Hayden and Stevens, 1990; Figure 5), and it inhibited basal and nystatin-stimulated QO2 (an indirect measure of state 3) in intact proximal tubules prior to the onset of cell death (Groves et al., 1993). However, iron-mediated lipid peroxidation had a minimal role in TFEC-induced cell death (Groves et al., 1991; Table 3).
Phonosurgery
Published in John C Watkinson, Raymond W Clarke, Terry M Jones, Vinidh Paleri, Nicholas White, Tim Woolford, Head & Neck Surgery Plastic Surgery, 2018
Teflon is a polymer of tetrafluoroethylene and is sold as a paste consisting of 50% glycerine. The glycerine component is absorbed in the first few weeks and its volume is partially replaced initially by an acute inflammatory reaction and later by a localized chronic inflammatory response, which encapsulates the remaining Teflon. This is, in effect, a localized granuloma but the difference in the initial volume injected and the final space-occupying lesion is unpredictable, which may cause a good immediate result to deteriorate with time. If Teflon is incorrectly placed superficially and erosion of the overlying mucosa occurs, this can lead to a granuloma on the surface of the vocal fold, and a 36% incidence of granuloma production has been reported. Teflon particle sizes in the paste are sold as 50–100 microns, too large for immediate lymphatic spread since macrophage lymphatic cut-off is 40 microns. Studies on a commercial preparation of Teflon, however, have found particles of 4–40 microns, which must lead to the question of distal spread. A study on Teflon injection into the peri-urethral areas has shown spread to both regional and distal organs via venous channels, but although local spread to lymph nodes and the thyroid gland has been demonstrated with laryngeal injection, no distal spread has yet been documented.
Endovascular intervention for renal artery occlusive disease
Published in Sachinder Singh Hans, Alexander D Shepard, Mitchell R Weaver, Paul G Bove, Graham W Long, Endovascular and Open Vascular Reconstruction, 2017
Jason Q. Alexander, Derrick Green, Timothy M. Sullivan
More often, the best chance of percutaneous revascularization is via cannulation of the covered artery from a brachial approach. The lay of the graft makes a femoral approach of limited utility. Even when the RA can be accessed from the brachial artery, considerable effort may be exhausted maintaining position. Early placement of a long sheath before RA selection can be helpful, because maintaining access can be tenuous and easily lost when a sheath is being advanced after RA selection. Constant vigilance is necessary to prevent loss of access to the RA. Intuitively, increased radial strength in the stent makes sense. Thus, a first choice would be a balloon-expandable covered stent. However, data from early reviews of the chEVAR literature suggests that it may be best to match a covered stent with the type/material of the endograft placed. Fewer subsequent endoleaks appear to be present when self-expanding nitinol stents are matched with similar grafts (e.g., GO RE-TEX®/poly tetrafluoroethylene grafts) while balloon-expandable stents may work more favorably with other endograft options (e.g., woven/polyethylene terephthalate grafts). Future studies may help to clarify the juxtaposition of these stents. Regardless, overlap of the stent into the aorta and ideally well above the top of the endograft is likely beneficial to prevent recurrence or stent thrombosis (Figures4.9and4.10).
Potential applications of mesenchymal stem cells and their derived exosomes in regenerative medicine
Published in Expert Opinion on Biological Therapy, 2023
Maryam Adelipour, David M. Lubman, Jeongkwon Kim
Since both synthetic and biomaterials are extensively used in tissue repair and therapeutic procedures, material development is a high priority in regenerative medicine. Although some synthetic materials, such as silicone and tetrafluoroethylene, were developed to repair damaged tissues, their tissue-specific functional characteristics were not preserved [3]. Therefore, in recent decades, living materials that are biologically generated by living cells have been of great interest due to their ability to be well-tolerated by the body and to promote biological activity [1]. To develop living materials, human cells, especially those with the potential for self-renewal, expansion, and differentiation into other types of cells, have been a crucial focus in the field of regenerative medicine [4].
Critical review of renal tubule karyomegaly in non-clinical safety evaluation studies and its significance for human risk assessment
Published in Critical Reviews in Toxicology, 2018
The lack of robust correlation between karyomegaly and RTT development in rat and mouse is also underscored by certain chemicals in the NTP testing series. The non-genotoxic fluorocarbon, tetrafluoroethylene, induced karyomegaly in male and female mice but did not induce RTT. In contrast, this compound induced renal tubule hyperplasia and RTT in male and female rats, but was not listed as producing karyomegaly in the tabulation of the kidney non-neoplastic lesions in either sex of rat in the NTP report (NTP 1997). Similarly, the flame retardant, tris(2-chloroethyl) phosphate induced approximately a 50% incidence of renal tubule adenomas in both male and female rats but did not induce karyomegaly. On the other hand, this compound induced renal tubule karyomegaly in both sexes of mice, but on standard evaluation of the kidneys, no increase in RTT. Upon step-sectioning evaluation, the tumor count increased in the high-dose males to 8%, representing only a marginal but not statistically significant increase compared to the control tumor incidence of 2% (NTP 1991a).
Off-the-shelf tissue engineered heart valves for in situ regeneration: current state, challenges and future directions
Published in Expert Review of Medical Devices, 2018
Sarah E. Motta, Valentina Lintas, Emanuela S. Fioretta, Simon P. Hoerstrup, Maximilian Y. Emmert
Alternatively to bioprosthetic or mechanical valves, synthetic nonbiodegradable heart valves for surgical or catheter-based techniques have been explored since the 1950s, but have not been included in clinical routine [13]. Among the various approaches reported in literature, recent studies concerning the in vivo performance of poly(carbonate urea) [14] or poly(tetrafluoroethylene)-based [15] valves showed controversial outcomes, mainly because of their tendency to calcify, stiffen, or undergo mechanical failure. Poly(urethane) surgical valves, when implanted in vivo in the ovine or porcine model, experienced thrombus formation, mild calcification, cusp thickening, and regurgitation [16–18]. Conversely, poly(styrene-b-isobutylene-b-styrene) valves, initially reported to undergo calcification and thrombus formation in the sheep [19], have been recently improved and showed reduced thrombogenicity and promising hemodynamic profiles [20]. However, in order to optimize the material resistance to in vivo deterioration and thus reduce the risk for structural failure, future studies should investigate novel strategies to improve the material stability and avoid excessive material degradation in vivo.