Repair of nerve injury by implanting prostheses obtained from isogenic acellular nerve segments. / Reparación de lesiones en nervios mediante el implante de prótesis obtenidas de segmentos acelulares de nervio isogénico.

INTRODUCTION: When a nerve section with a significant gap occurs, it is necessary to use a prosthesis to suture it. To date an autologous nerve segment graft appears to be the best treatment; but it has several important disadvantages. Our goal is to study the effectiveness of an isogenic acellular nerve prosthesis comparing a simple suture with tubulisation. MATERIAL AND METHOD: Four groups of Wistar rats were used. The animals in Group 0 served as donors of nerve segments to graft. Group 1 received the implant with an end-to-end suture. In group 2, the implant was sutured inside an ɛ-caprolactone tube. Group 3 received it in a polylactic-co-glycolic acid tube. We evaluated the motor function (sciatic index and step test in motion), and the regeneration length by histological study of regeneration, after a maximum of 3 weeks. RESULTS: Regeneration was uneven in the three groups. In all groups, there were implants with regenerated nerve fibres at the maximum studied length (15mm) and others where regeneration was scarce. The mean regeneration length was greater in the direct end-to-end suture group (G1), although the regeneration speed was similar in the three groups. Group 1 showed the highest percentage of regeneration, but the variability of results prevents this difference reaching statistical significance. We found no significant differences between the two groups with polymer tubes. CONCLUSION: For the implantation of isogenic acellular nerve prosthesis, under our experimental conditions, the direct end-to-end suture was more effective than when it isprotected with biopolymer tubes.

Recyclable islet isografts: a biological insulin pump to facilitate surgery in diabetic rats.

A method is described to facilitate extensive abdominal surgery in diabetic rats using temporary renal subcapsular islet isografts. The procedure is performed in three stages--each separated by 2 wk. After each rat is made diabetic (Step 1), an isogenic islet transplant is performed beneath the left renal capsule (Step 2). Step 3 is the operative procedure, followed by a left nephrectomy. Finally, it is shown how the islet isograft can be excised from the nephrectomy specimen and "recycled" into another diabetic rat (Step 2). Using this three step process, it is possible to decrease the mortality rate following orthotropic liver transplantation in diabetic rats from 100% to about 30%. This procedure can also be used to facilitate other extensive surgical procedures in diabetic rats.

Problems in the use of polycarbonate diffusion chambers for syngeneic pancreatic islet transplantation in rats.

Islets of Langerhans have been enclosed in polycarbonate diffusion chambers and transplanted intraperitoneally to syngeneic streptozotocin diabetic rats. Direct implantation of 1100--1400 islets in these chambers failed to reverse diabetes during a period of 12 weeks, and viable islet tissue was not recoverable at the end of this period. Islets placed in chambers which had been implanted 3--12 weeks previously similarly failed to lower blood glucose of diabetic recipients, as a result of lack of survival of the islets. Insulin infusion into chambers previously implanted in vivo, I125 insulin diffusion studies in chambers recovered 6--8 weeks after implantation, and scanning electron microscopy of the recovered membranes all indicated that the pores were not totally occluded. The failure of islet transplantation via chambers in this simple syngeneic model has discouraging implications for their use as a means of avoiding allograft rejection.