Three cases are reported to illustrate the potential danger of silicon-polymer intubulation of nerve for either nerve repair or following neurolysis. Since silicon-polymer intubulation of nerve is now a proven model for producing chronic nerve compression, its use clinically may be contraindicated where neural regeneration is the desired goal.

Combined traumatic brain injury (TBI) and hemorrhagic shock (HS) remains a leading cause of preventable death worldwide. Mesenchymal stem cell-derived exosomes have demonstrated promise in small animal models of neurologic injury. To investigate the effects of exosome treatment in a clinically realistic large animal model, Yorkshire swine underwent TBI and HS. Animals were maintained in shock for 2 h before resuscitation with normal saline (NS). Animals were then resuscitated either with NS (3 × volume of shed blood) or with the same volume of NS with delayed exosome administration (1 × 10 particles/4 mL) (n = 5/cohort). Exosomes were administered 9 h post-injury, and on post-injury days (PID) 1, 5, 9, and 13. Neurologic severity scores (NSS) were assessed for 30 days, and neurocognitive functions were objectively measured. Exosome-treated animals had significantly lower NSS (p < 0.05) during the first five days of recovery. Exosome-treated animals also had a significantly shorter time to complete neurologic recovery (NSS = 0) compared with animals given NS alone (days to recovery: NS = 16.8 ± 10.6; NS + exosomes = 5.6 ± 2.8; p = 0.03). Animals treated with exosomes initiated neurocognitive testing earlier (days to initiation: NS = 9.6 ± 0.5 vs. NS + exosomes = 4.2 ± 0.8; p = 0.008); however, no difference was seen in time to mastery of tasks. In conclusion, treatment with exosomes attenuates the severity of neurologic injury and allows for faster neurologic recovery in a clinically realistic large animal model of TBI and HS.

Peripheral nerve gap defects lead to significant loss of sensory or motor function. Tissue engineering has become an important alternative to nerve repair. Sericin, a major component of silk, is a natural protein whose value in tissue engineering has just begun to be explored. Here, the first time use of sericin in vivo is reported as a long-term implant for peripheral nerve regeneration. A sericin nerve guidance conduit is designed and fabricated. This conduit is highly porous with mechanical strength matching peripheral nerve tissue. It supports Schwann cell proliferation and is capable of up-regulating the transcription of glial cell derived neurotrophic factor and nerve growth factor in Schwann cells. The sericin conduit wrapped with a silicone conduit (sericin/silicone double conduits) is used for bridging repair of a 5 mm gap in a rat sciatic nerve transection model. The sericin/silicone double conduits achieve functional recovery comparable to that of autologous nerve grafting as evidenced by drastically improved nerve function and morphology. Importantly, this improvement is mainly attributed to the sericin conduit as the silicone conduit alone only produces marginal functional recovery. This sericin/silicone-double-conduit strategy offers an efficient and valuable alternative to autologous nerve grafting for repairing damaged peripheral nerve.

JEL classification: F13 F14 C14 C21 C23 Keywords: Trade flow Treatment effect Matching Permutation test Signed-rank test Sensitivity analysisThis paper re-examines the GATT/WTO membership effect on bilateral trade flows, using nonparametric methods including pair-matching, permutation tests, and a Rosenbaum (2002) sensitivity analysis. Together, these methods provide an estimation framework that is robust to misspecification bias, allows general forms of heterogeneous membership effects, and addresses potential hidden selection bias. This is in contrast to most conventional parametric studies on this issue. Our results suggest large GATT/WTO trade-promoting effects that are robust to various restricted matching criteria, alternative GATT/WTO indicators, non-random incidence of positive trade flows, inclusion of multilateral resistance terms, and different matching methodologies.