Chen, Lin

Total implantable venous access port (TIVAP) by cephalic vein cutdown (CVCD) is one of the first procedures surgery residents can be performed independently under supervision. There is currently a lack of affordable simulators for teaching and assessing TIVAP competency to improve patient safety. A panel of 10 experts divided the TIVAP by CVCD procedure into 9 steps. A homemade, low-cost ($3 USD) simulator was then designed for practicing standardized procedural steps in the context of a simulation-based mastery learning course. Residents were given a simulator for at-home practice and completed a survey evaluating the simulator and their learning experience. Twenty-eight first-year surgery residents participated in the course and completed the survey. They were highly satisfied with the simulator (mean score = 8.7 of 10) and generally agreed with its anatomical appearance and functional fidelity. They also appreciated the educational value of using this simulator to learn and practice basic techniques and procedural steps. Our novel, homemade simulator of CVCD TIVAP implantation is a cost-effective way of achieving procedural competence of a basic operation for inexperienced surgery residents. We envision the same principle can be applied to other procedures to enhance resident education.

The crystal structure of a pentameric α7 ligand-binding domain chimaera with bound α-btx (α-bungarotoxin) showed that of the five conserved aromatic residues in α7, only Tyr184 in loop C of the ligand-binding site was required for high-affinity binding. To determine whether the contribution of Tyr184 depends on local residues, we generated mutations in an α7/5HT3A (5-hydroxytryptamine type 3A) receptor chimaera, individually and in pairs, and measured 125I-labelled α-btx binding. The results show that mutations of individual residues near Tyr184 do not affect α-btx affinity, but pairwise mutations decrease affinity in an energetically coupled manner. Kinetic measurements show that the affinity decreases arise through increases in the α-btx dissociation rate with little change in the association rate. Replacing loop C in α7 with loop C from the α-btx-insensitive α2 or α3 subunits abolishes high-affinity α-btx binding, but preserves acetylcholine-elicited single channel currents. However, in both the α2 and α3 construct, mutating either residue that flanks Tyr184 to its α7 counterpart restores high-affinity α-btx binding. Analogously, in α7, mutating both residues that flank Tyr184 to the α2 or α3 counterparts abolishes high-affinity α-btx binding. Thus interaction between Tyr184 and local residues contributes to high-affinity subtype-selective α-btx binding.