Microsurgery
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The peripheral nervous system retains a considerable capacity for regeneration. However, functional recovery rarely returns to the preinjury level no matter how accurate the nerve repair is, and the more proximal the injury the worse the recovery. ⋯ In this review article we focus on the roles in peripheral nerve regeneration of Schwann cells and of the neurotrophin family, CNTF and GDNF, and the relationship between these. Finally, we discuss what remains to be understood about the possible clinical use of neurotrophic factors.
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Comparative Study
Drug-induced vasodilation: in vitro and in vivo study on the effects of lidocaine and papaverine on rabbit carotid artery.
Flap ischemia is often encountered during pedicled and free tissue transfer. In this study, the vascular effects of varying doses of lidocaine, papaverine, and a combination of the two agents were evaluated and compared in an in vitro and in vivo model in the rabbit carotid artery. In the in vitro study, 14 rings from the rabbit carotid artery were bathed in Krebs-Ringers solution and stretched progressively to an optimal tension of 3.7-4.2 grams. ⋯ These results demonstrate that topical lidocaine 20%, papaverine, and lidocaine 2% or 20% combined with papaverine significantly increase blood flow in the rabbit carotid artery after microvascular anastomosis. The data confirm the use of papaverine and lidocaine 20%, alone or in combination, as spasmolytics during clinical microsurgery. This suggests that lidocaine 2% alone is not the ideal drug to relieve vascular constriction, and further studies on the clinical use of low concentrations of topical lidocaine in microsurgery is warranted.
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Hyaluronic acid has been shown to enhance peripheral nerve regeneration in vitro. It has been proposed that, during the fibrin matrix phase of regeneration, hyaluronic acid organizes the extracellular matrix into a hydrated open lattice, thereby facilitating migration of the regenerating axons. Hyaluronic acid solutions and saline control solutions were injected into a nerve guide spanning a transected gap in the sciatic nerve of Sprague-Dawley rats (five in each group). ⋯ After the animals were sacrificed, regenerated axon cables were quantified histologically, and axon branching was delineated by retrograde tracer analysis. In addition, the hyaluronic acid group showed an increase in myelinated axon counts at 4 weeks (P= 0.03). An increase in retrograde flow was demonstrated in the hyaluronic acid groups compared with animals receiving saline solution.
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Traditionally, the mouse nonvascularized skin graft has been widely used in organ transplant research. There are, however, several limitations with this model, the main one being the different immune response of vascularized vs. nonvascularized grafts. We have recently developed a vascularized, orthotopic ear transplant model in mice. ⋯ In summary, this study illustrates that it is technically possible to transplant a mouse ear graft. The main advantage of this model is that it is a vascularized graft that can be visibly observed and easily biopsied, thus allowing for good correlation between gross and histological findings after transplantation. We plan to use this model further to study in detail the rejection patterns in an allograft and xenograft setting.