Polytetrafluoroethylene-encapsulated stent-grafts: use in experimental abdominal aortic aneurysm.

PURPOSE: To evaluate expanded polytetrafluoroethylene (ePTFE) encapsulated stents for the treatment of aortic aneurysms with emphasis on the blood and tissue-material interactions. MATERIALS AND METHODS: Experimental aortic aneurysms were created in dogs by enlarging the aortic lumen with an abdominal fascial patch. Twenty animals underwent endoluminal repair after allowing the surgically created aneurysm to heal for 2 months prior to transluminal aneurysmal exclusion. The device used consisted of an 8-cm-long ePTFE encapsulated stent graft. The animals were killed in groups at 1 week and at 1, 2.25, 6, and 12 months. Specimens were processed for histologic and luminal surface studies. RESULTS: Before the animals were killed, aortography demonstrated two thrombosed aortae in the 6-month group and two endoleaks in the 12-month group. Endothelialized neointima extended into the proximal and distal portions of the prosthetic lumen, with minimal cell coverage in the center of the graft. The overall percent surface area covered by endothelialized neointima was 22% +/- 6% at 6 months and 18% +/- 10% by 1 year (P = .75). Histologic examination demonstrated minimal tissue penetration into the ePTFE. CONCLUSION: Transluminal exclusion of abdominal aortic aneurysms by encapsulated stent-graft is easily accomplished. With this device, tissue coverage and penetration of the stent graft is limited and does not tend to increase with time.

Embryonic hippocampal grafts ameliorate the deficit in DRL acquisition produced by hippocampectomy.

Transplants of fetal neural tissue survive and develop in lesion cavities produced in adult rats. The present experiment tested the effect of grafting fetal hippocampal or brainstem tissue on the ability of rats with hippocampal lesions to perform on a differential reinforcement of low response rate (DRL) operant schedule. The DRL interval was 20s. Eighty-six percent of the hippocampal grafts and 69% of the brainstem grafts developed to maturity. Inspection of sections from rats in which the mature transplant had been injected with Fast blue, indicated that these grafts formed connections with the host brain. Consistent with previous reports, rats with hippocampal lesions were impaired in performance of the DRL task. Rats given fetal grafts of hippocampal tissue into the hippocampal lesion site on the day of lesion production were significantly better in performance of the DRL requirement than were lesion-only rats or rats receiving grafts of fetal brainstem tissue. The results of this study confirm that grafts of fetal brain tissue can both develop in a lesion site in an adult brain and ameliorate lesion-induced behavioral deficits.

Cells of origin of the branches of the facial nerve: a retrograde HRP study in the rabbit.

The origin of different branches of the facial nerve in the rabbit was determined by using retrograde transport of HRP. Either the proximal stump of specific nerves was exposed to HRP after transection, or an injection of the tracer was made into particular muscles innervated by a branch of the facial nerve. A clear somatotopic pattern was observed. Those branches which innervate the rostral facial musculature arise from cells located in the lateral and intermediate portions of the nuclear complex. Orbital musculature is supplied by neurons in the dorsal portion of the complex, with the more rostral orbital muscles receiving input from more laterally located cells while the caudal orbital region receives innervation from more medial regions of the dorsal facial nucleus. The rostral portion of the ear also receives innervation from cells located in the dorsomedial part of the nucleus, but the caudal aspect of the ear is supplied exclusively by cells located in medial regions. The cervical platysma, the platysma of the lower jaw, and the deep muscles (i.e., digastric and stylohyoid) receive input from cells topographically arranged in the middle and ventral portions of the nuclear complex. It is proposed that the topographic relationship between the facial nucleus and branches of the facial nerve reflects the embryological derivation of the facial muscles. Those muscles that develop from the embryonic sphincter colli profundus layer are innervated by lateral and dorsomedial portions of the nuclear complex. The muscles derived from the embryonic platysma layer, including the deep musculature, receive their input from mid to ventral regions of the nuclear complex.

The motor innervation of the single-bellied digastric muscle in the rabbit: a retrograde horseradish peroxidase study.

The digastric muscle of the rabbit consists of a single anterior belly which inserts onto the lower jaw. Horseradish peroxidase was injected into the muscle and into subcutaneous regions overlying the lower jaw to determine the sites of origin of the motor innervation to both the digastric muscle and the platysma muscles. After digastric muscle injection, labelled cells were found in the ipsilateral retrotrigeminal nucleus as well as in the intermediate subnucleus of the main facial nucleus on both sides. Subcutaneous injections produced labelling which was found bilaterally in the intermediate subnucleus and in the ventromedial portion of the medial subnucleus. These results are interpreted in relation to the common embryological origin of these two muscles and their innervation.