No abstract available.
Rabbits*

No abstract available.
Rabbits*

No abstract available.
Rabbits*

No abstract available.
Rabbits*

No abstract available.
Rabbits*

The authors studied the early morphologic changes of peripheral nerve, which is known as relatively radioresistant tissue to the X-ray irradiation, but recently clamied by several clinician through development of neuropathies after radiotherapy of the malignacy. Rabbits were received 1,000 or 2,000 cGy of X-ray on the knee joint areas. Sciatic nerves were extracted out 30 minutes, 1, 2, 4, 24 hours, and 3 and 7 days after irradiation. The morphologic changes were observed by light and electron microscopes. The results were summarized as follows: Light microscopically, only mild edema is noted. Electron microscopically, irregular separation and folding of myelin sheath with spherical body formation are noted. Above features were more prominent at later stages and aggregated nests of fragmented myelin were scattered 16 hours after irradiation. Schwann cell necrosis is noted after 24 hours. But above degenerative changes were scarcely present 7 days after irradiation. There is no remarkable axonal changes. The interstitial tissue revealed swelling and irregularity of surface of endothelial cells, and edema. On the basis of the results, it may be concluded that the peripheral nerve is injured by irradiation in early stages, and the main target of irradiation injury is thought to be myelin sheath and Schwann cells, which would be reversible and could be recovered promptly.
Rabbits ; Animals

The purpose of this study was to evaluate exophytically vertical bone formation in rabbit calvaria by the concept of guided bone regeneration with a custom-made porous titanium membrane combined with bone graft materials. For this purpose, a total of 12 rabbits were used, and decorticated calvaria were created with round carbide bur to promote bleeding and blood clot formation in the wound area. Porous titanium membranes (0.5 mm in pore diameter, 10 mm in one side, 2 mm in inner height) were placed on the decorticated calvaria, fixed with metal pins and covered with full-thickness flap. Experimental group I was treated as titanium membrane only. Experimental group II,III,IV was treated as titanium membrane with BBM, titanium membrane with DFDB and titanium membrane with FDB. The animals were sacrificed at 8 and 12 weeks after surgery, and new bone formation was assessed by histomorphometric as well as statistical analysis. 1. Porous titanium membrane was biocompatable and capable of maintaining the regeneration space. 2. At 8 and 12 weeks, all groups demonstrated exophytic bone formation and there was a statistical significant difference among different groups only at 12 weeks. 3. The DFDB group revealed the most new bone formation compared to other groups (p<0.05). 4. At 12 weeks, DFDB and FDB groups showed the most significant resorption of graft materials (p<0.05). 5. The BBM was not resorbed at all until 12 weeks. 6. The fixation metal pin revealed excellent effect in peripheral sealing. On the basis of these findings, we conclude that a porous titanium membrane may be used as an augmentation membrane for guided bone regeneration, and DFDB as an effective bone forming graft material. The fixation of the membrane with pin will be helpful in GBR technique. However, further study is required to examine their efficacy in the intraoral experiments.
Rabbits ; Animals

No abstract available.
Rabbits ; Animals

While calcium phosphate ceramics meet some of the needs for bone replacement, they have some limitation of unresorbability and fibrous encapsulation without direct bone apposition during bone remodelling. To address these problem, we developed a new ceramic, calcium metaphosphate(CMP), and report herein the biologic response to CMP in subcutaneous tissue, muscle and bone. Porous CMP blocks were prepared by condensation of anhydrous Ca(H2PO4)2 to form non-crystalline Ca(PO3)2. Macroporous scaffolds were made using a polyurethane sponge method. CMP block possesses a macroporous structure with approximate pore size range of 0.3-1mm. CMP blocks were implanted in 8 mm sized calvarial defect, subcutaneous tissue and muscle of 6 Newzealand White rabbits and histologic observation were performed at 4 and 6 weeks later. CMP blocks in subcutaneous tissue and muscle were well adapted without any adverse tissue reaction and resorbed slowly and spontaneously. Histologic observation of calvarial defect at 4 and 6 weeks revealed that CMP matrix were mingled with and directly apposed to new bone without any intervention of fibrous connective tissue. CMP blocks didn't show any adverse tissue reaction and resorbed spontaneously also in calvarial defect. This result revealed that CMP had a high affinity for bone and was very biocompatible. From this preliminary result, it was suggested that CMP was a promising ceramic as a bone substitute and tissue engineering scaffold for bone formation.
Rabbits ; Animals

Ketamine hydrochloride(ketamine) is a non-barbiturate anesthetic agent chemically designated as dl-2-(0-chlorophenyl)2-(methylamino)-cyclohexanone hydrochloride. Ketamine anesthesia has been found distinctively different from that induced by conventional anesthetic agents, as it provides profound analgesia without significant impairment of respiratory function or stimulation of cardiovascular activities thus avoiding hypotension and are preserved the protective pharyngeal and laryngeal reflexes. In addition, ketamine appears to have muscle relaxation properties. This latter clinical finding, however has not been experimentally substantiated since few reports have appeared on the effect of ketamine on muscle relaxation. The present study therefore, was undertaken to determine whether this agent affects the muscle activity during d-tubocurarine block. The experiment was performed on sixteen rabbits weighing 1.8 to 2.5kg and these were divided into two groups; eight rabbits for control and eight for th study group. All animals were intubated through a tracheostomy under general anesthesia with nembutal 40mg/kg given intravenously. Respiration was controlled by means of a Harvard animal respirator. The body temperature was kept at 35 degrees C to 36 degrees C with a thermo-blanket. The common peroneal nerve and anterior tibial muscle was exposed and the nerve stimulator was applied to the nerve muscle preparation. The twhitch height of the muscle contraction was recorded on a biophysiograph through the force displacement transducer. The common peroneal nerve was stimulated supramaximally using a single twitch, square wave of 0.2 msec duration at a frequency of 0.1Hz once every 10 seconds. The degree of neuromuscular block following intravenous injection of d-tubocurarine 1mg/kg was measured in the control group. And in the study group ketamine 5mg/kg was administered intravenously when 25% of twitch height of muscle contraction was obtained spontaneously after the intravenous injection of d-tubocurarine 1mg/kg. The changes of the twitch height of muscle contraction and the time of spontaneous recovery in the study group were compared with those of the control group. The results were as follows: 1) The times and degree of maximal single twitch depression were obtained at 194.8sec and 87.3% in the control group and were at 197.5 sec and 87.8% in study group. No significant difference was observed. 2) Recovery index of the control group was 1,560.0 sec and recovery index of the study group was markedly prolonged to 2,387.5 sec(53.0% prolongation). 3) Mean decrease of single twitch height was 8.8% soon after the intravenous ketamine 5mg/kg when 25% of twitch height was obtained after the intravenous d-tubocurarine 1mg/kg in the study group.
Rabbits ; Animals