Biomedical Engineering
Biomedical Engineering - Open Access Policy Deposits (5090)
Noninvasive Measurement of Ablation Crater Size and Thermal Injury after CO2 Laser in the Vocal Cord with Optical Coherence Tomography
Objective
To characterize tissue destruction after CO(2) laser-ablation of the vocal cords with the use of optical coherence tomography (OCT).Study design and setting
OCT was used to image fresh porcine vocal cords after laser ablation. OCT and histology estimates of the ablation crater dimensions and the depth of thermal injury were obtained.Results
The vocal cord substructures up to 2.29 mm in depth at 10 microm resolution, and the thermal disruption after laser ablation were identified by OCT. OCT and histology estimates of the lesion dimensions showed no significant differences. Crater depth is directly proportional to laser power, whereas crater width and the zone of thermal injury appear to be unrelated to laser power.Conclusions
OCT may be used to accurately characterize the native states and the laser-induced thermal injury of laryngeal mucosa, within the inherent limitation in its depth of penetration. OCT may be a useful diagnostic and monitoring tool in an otolaryngology practice.Histologic changes associated with talaporfin sodium-mediated photodynamic therapy in rat skin.
Background and objective
Alternative treatments are needed to achieve consistent and more complete port wine stain (PWS) removal, especially in darker skin types; photodynamic therapy (PDT) is a promising alternative treatment. To this end, we previously reported on Talaporfin Sodium (TS)-mediated PDT. It is essential to understand treatment tissue effects to design a protocol that will achieve selective vascular injury without ulceration and scarring. The objective of this work is to assess skin changes associated with TS-mediated PDT with clinically relevant treatment parameters.Study design/materials and methods
We performed TS (0.75 mg/kg)-mediated PDT (664 nm) on Sprague Dawley rats. Radiant exposures were varied between 15 and 100 J/cm2 . We took skin biopsies from subjects at 9 hours following PDT. We assessed the degree and depth of vascular and surrounding tissue injury using histology and immunohistochemical staining.Results
TS-mediated PDT at 0.75 mg/kg combined with 15 and 25 J/cm2 light doses resulted in vascular injury with minimal epidermal damage. At light dose of 50 J/cm2 , epidermal damage was noted with vascular injury. At light doses >50 J/cm2 , both vascular and surrounding tissue injury were observed in the forms of vasculitis, extravasated red blood cells, and coagulative necrosis. Extensive coagulative necrosis involving deeper adnexal structures was observed for 75 and 100 J/cm2 light doses. Observed depth of injury increased with increasing radiant exposure, although this relationship was not linear.Conclusion
TS-mediated PDT can cause selective vascular injury; however, at higher light doses, significant extra-vascular injury was observed. This information can be used to contribute to design of safe protocols to be used for treatment of cutaneous vascular lesions. Lasers Surg. Med. 49:767-772, 2017. © 2017 Wiley Periodicals, Inc.RNA Binding and Core Complexes Constitute the U-Insertion/Deletion Editosome
Enzymes embedded into the RNA editing core complex (RECC) catalyze the U-insertion/deletion editing cascade to generate open reading frames in trypanosomal mitochondrial mRNAs. The sequential reactions of mRNA cleavage, U-addition or removal, and ligation are directed by guide RNAs (gRNAs). We combined proteomic, genetic, and functional studies with sequencing of total and complex-bound RNAs to define a protein particle responsible for the recognition of gRNAs and pre-mRNA substrates, editing intermediates, and products. This approximately 23-polypeptide tripartite assembly, termed the RNA editing substrate binding complex (RESC), also functions as the interface between mRNA editing, polyadenylation, and translation. Furthermore, we found that gRNAs represent only a subset of small mitochondrial RNAs, and yet an inexplicably high fraction of them possess 3' U-tails, which correlates with gRNA's enrichment in the RESC. Although both gRNAs and mRNAs are associated with the RESC, their metabolic fates are distinct: gRNAs are degraded in an editing-dependent process, whereas edited mRNAs undergo 3' adenylation/uridylation prior to translation. Our results demonstrate that the well-characterized editing core complex (RECC) and the RNA binding particle defined in this study (RESC) typify enzymatic and substrate binding macromolecular constituents, respectively, of the ∼40S RNA editing holoenzyme, the editosome.