An Identification and Characterization of the Axolotl (Ambystoma mexicanum, Amex) Telomerase Reverse Transcriptase (Amex TERT).

The Mexican axolotl is one of the few vertebrates that is able to replace its lost body parts during lifespan. Due to its remarkable regenerative abilities, the axolotl emerged as a model organism especially for limb regeneration. Telomeres and the telomerase enzyme are crucial for regeneration and protection against aging processes and degenerating diseases. Despite its relevance for regeneration, the axolotl telomerase and telomere length have not yet been investigated. Therefore, in the present paper, we reveal the sequence of the axolotl telomerase reverse transcriptase gene (Tert) and protein (TERT). Multiple sequence alignment (MSA) showed the known conserved RT- and TERT-specific motifs and residues found in other TERTs. In addition, we establish methods to determine the Tert expression (RT-PCR) and telomerase activity (Q-TRAP) of adult axolotl and blastema tissues. We found that both differentiated forelimb tissue and regenerating blastema tissue express Tert and show telomerase activity. Furthermore, blastema tissue appears to exhibit a higher Tert expression and telomerase activity. The presence of active telomerase in adult somatic cells is a decisive difference to somatic cells of non-regenerating vertebrates, such as humans. These findings indicate that telomere biology may play a key role in the regenerative abilities of cells.

CAD/CAM-based referencing aids to reduce preoperative radiation exposure for intraoperative navigation.

BACKGROUND: All intraoperative navigation systems need a referencing procedure prior to utilization, usually requiring an additional computed tomography (CT) or cone beam computed tomograph (CBCT) scan. As new techniques in the field of Computer-aided design / Computer-aided manufacturing (CAD/CAM) have evolved, it seemed favourable to develop a new referencing method not relying on additional CT or CBCT scans. METHODS: A digital maxillary dental scan was used to create a referencing splint by CAD/CAM containing four reference points. By matching scanned dental model and initial trauma-CT, the splints position and thus the reference points were digitally simulated. These splints data were imported into the navigation system in Standard Tessellation Language (STL) format. These data were also 3D printed and the resulting piece was placed on the anatomical models' teeth. The methods accuracy was then assessed in vitro. CONCLUSION: Our method for referencing of intraoperative navigation can be feasible to avoid an additional CT or CBCT prior to navigation.