Isolation and identification of narcotics by thin layer chromatography. 4. Isolation and identification of narcotics in carbon monoxide poisoning.
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Animals↗
Biomedical subjects
T Kiyotani
Publications and source records attributed to T Kiyotani.
A new thermal shape memory Ti-Ni alloy stent covered with silicone.
An attempt was made to develop an airway stent for nonsurgical transluminal implantation using a bronchofiberscope. The stent is composed of a single wire with a diameter of 0.5 mm. The wire is made of thermal shape memory titanium nickel alloy, with a transition temperature of 25-30 degrees C. To avoid direct contact between the metal and the tissue, the wire is covered with a 300 microns thick coating of silicone. The stent is horseshoe shaped in cross-section. It is 15 mm in outer transverse diameter and 40 mm long. Ten stents were implanted in 10 dogs whose tracheal cartilages had been previously broken. The stents were first cooled in ice water to reduce their diameter and then inserted into the target site. The wire was warmed to body temperature and recovered its initial shape within 10 sec. The dogs were killed for examination between 1 week and 6 months after implantation. All the stents were located at the implantation sites and were patent. Tissue reactions, such as ulceration and granulation formation, were less severe than in those with previously implanted non-silicone covered stents. Microscopic observation showed that the wires became gradually covered with epithelium within 2 months. This transluminal technique for preserving airway patency shows promise for clinical application.
Alloys↗
The repair of tracheal defects using bioabsorbable mesh.
This study compares the use of synthetic bioabsorbable mesh with that of non-absorbable mesh in repairing tracheal defects. Two patch windows, each 1 cm x 1 cm, were created on the ventral wall of the cervical trachea in 12 adult mongrel dogs. One window was repaired using a bioabsorbable polyglycolic acid (PGA) mesh graft, and the other using a nonabsorbable Marlex mesh (polypropylene mesh; PP mesh) (C. R. Bard, Inc., Billerica, MA) graft. The dogs were killed at intervals from 1 to 35 weeks after surgery. Macroscopically, there was no difference between the two mesh groups until 3 weeks after surgery. At 6 weeks in the PP mesh group, the connective tissue over the mesh was remarkably thick, and after 9 weeks, constriction by scarlike tissue was evident, as compared with the PGA mesh group, which showed no constriction. Microscopically, epithelium covered the whole mesh in both groups at 6 weeks. However, in the PP mesh group, flat and poorly differentiated cells occupied a large area, and after 9 weeks the height of the epithelial cells in the PP mesh group was less than in the PGA mesh group. Furthermore, in the PP mesh group, nonciliated cells occupied a large area even at 15 weeks, and the submucous connective tissue layer was thicker than in the PGA mesh group after 6 weeks. The results indicate that, from the point of view of wound-healing, bioabsorbable mesh may be more adequate for repairing tracheal defects.
Absorption↗
A new porous tracheal prosthesis sealed with collagen sponge.
We have designed a new tracheal prosthesis to overcome problems with an earlier device, which included stenosis and exposure of its constituent mesh. A polypropylene mesh cylinder, reinforced with a polypropylene spiral, is sealed with collagen sponge made from porcine dermal collagen. Using this prosthesis, we performed cervical tracheal reconstructions on 11 dogs. Three dogs died within 3 months of reconstruction. Their causes of death were anesthetic accident, diarrhea, and suffocation, respectively. Bronchoscopically, the inner surface of the prosthesis was almost covered with host tissue by 2 months. However, in one dog, a relatively large area of the mesh was exposed in the tracheal lumen at 6 months; a smaller area was exposed in two other dogs. The appearance of the inner surface rapidly became lustrous, and central stenosis was not significant, even after 12 months. Histologically, an incomplete epithelial lining at 6 months was seen on the reconstructed surface and included ciliated columnar, cuboidal, and squamous epithelium. These observations have revealed that this prosthesis has high biocompatibility and the potential to overcome problems of stenosis of the prosthesis lumen. However, because ulceration persists with this prosthesis, additional improvement is needed to reduce the incidence of mesh exposure.
Animals↗
Replacement of long segments of the esophagus with a collagen-silicone composite tube.
Artificial esophagi designed thus far can be classified into three types in terms of the materials used: natural, artificial, and composite. In conventional models, even when artificial esophagi were made of ideal materials with high tissue affinity, they remained in the tissue as a foreign body, and therefore were not free of the complications caused by implanted material. The authors have designed a new type of artificial esophagus composed of a Silicone tube covered with nonantigenic collagen. The novel feature of this artificial esophagus is that the prosthesis does not remain in the implanted site, but is replaced by regenerated host tissue. Using this artificial esophagus, the authors have already succeeded in replacing a 5 cm gap in the esophagus. In this study, replacement of longer portions of the esophagus was assessed in seven dogs using a 10 cm long artificial esophagus. Stenosis did not occur in five of the seven dogs and, consequently, these dogs survived by oral feeding alone for more than 6 months without dry weight loss. The other two animals died of anesthetic accidents at the time of stent removal 6 weeks after surgery. In both cases, the internal surface of the neoesophagus was covered with a polylayer of squamous epithelium. Regenerated esophagi had normal esophageal glands and immature muscle tissue. It is therefore concluded that this new artificial esophagus is also applicable for replacement of long segments of esophagus.
Animals↗
Experimental study of nerve regeneration in a biodegradable tube made from collagen and polyglycolic acid.
The authors developed a novel bioabsorbable nerve conduit to induce nerve regeneration across long gaps. It is a composite tube made of polyglycolic acid mesh coated with collagen. Seven cats underwent 25 mm resection of the left sciatic nerve. The proximal and distal nerve stumps were inserted into the tube and fixed with sutures to bridge the 25 mm gap between them. Histologic examination 4 months after implantation of the tube showed regeneration of nerve tissue structure, including myelinated axons and Schwann cells, and somatosensory evoked potentials and electromyograms demonstrated functional recovery of the regenerated nerves. Horseradish peroxidase staining revealed restoration of anterograde and retrograde axonal transport. These results indicate that this polyglycolic acid-collagen composite tube is promising as a nerve conduit that provides adequate nerve regeneration.
Afferent Pathways↗
Replacement of the tracheobronchial bifurcation by a newly developed Y-shaped artificial trachea.
We have previously reported on a straight artificial trachea developed by our group that can be applied to the cervical and thoracic trachea. In this study, a new Y-shaped artificial trachea was designed and adapted for experimental replacement of defective tracheal bifurcations in 20 dogs. The Y-shaped Marlex mesh tube was reinforced with a polypropylene spiral and coated with collagen made from porcine skin. This coating process makes the prosthesis biocompatible and airtight. Replacement of the tracheobronchial bifurcation was performed through a right thorachotomy, and omentopexy was added in all 20 dogs. Six of the 20 dogs have survived. The causes of death of the other 14 dogs were obstruction of the main bronchus (one dog), omental necrosis (three dogs), and air leakage from the prostheses and suture points (10 dogs). In all six surviving dogs, the artificial tracheas are covered with regenerated tissue and there is no evidence of stenosis or dehiscence. These results indicate that the prosthesis can be effective and safe in the long-term; however, air leakage from the prosthesis is a serious complication. Therefore, a better method is needed to make the prosthesis airtight to improve the postoperative result.
Animals↗
A novel surgical material made from collagen with high mechanical strength: a collagen sandwich membrane.
We have developed a novel collagen membrane with excellent mechanical properties using a new method and examined its breaking strength, microstructure, and absorption behavior in vivo. Types I and III atelopeptide collagen extracted from porcine skin by treatment with pepsin were used. One volume percent collagen hydrochloride solution, pH 3.0, was frozen in a cast, then freeze-dried and pressed. Both surfaces of the resulting membrane were coated with 2% w/v collagen hydrochloride solution, pH 3.0, and dried. This procedure was then repeated 10 times, and the membrane was finally heated in vacuo. Microstructural observation showed that the inner part of the membrane consisted of piles of thin collagen nonwoven fabric layers, whereas the coated surface consisted of an amorphous collagen layer. The breaking strength of this membrane with a thickness of 0.5 mm was 73.5 N/cm in dry conditions. The mechanical strength of the membrane was 3.4 to 10.8 times greater than that of control membranes that had not been subjected to coating procedures. The absorption of this membrane was investigated by an implantation test in rabbits. The absorption rate of the membrane in vivo was similar to that of the noncoated control material, and only minimal tissue reaction was evident. Because the mechanical properties of this membrane, made from only collagen, are adequate for suturing without reinforcement by other materials, and its absorption in vivo has so far been equal to that of collagen membranes, the membrane is potentially applicable for various surgical uses such as replacement of tissue defects.
Absorption↗
Experimental replacement of the thoracic esophagus with a bioabsorbable collagen sponge scaffold supported by a silicone stent in dogs.
We manufactured an esophageal prosthesis made of a collagen sponge supported by an inner silicone tube. The collagen was derived from porcine skin and was crosslinked by dehydrothermal treatment. We implanted our prosthesis in nine dogs after resecting a 5 cm length of the thoracic esophagus. Intravenous hyperalimentation was performed for 4 weeks after the surgery. After 29 days, the inner silicone tube was removed endoscopically and oral feeding was restarted immediately. All nine dogs survived more than 1 month, and three of the nine dogs survived for more than 1 year. Endoscopically, the luminal surface of the regenerated esophagus was covered with a lustrous, smooth mucosa, but stenosis was observed in the midregion of the regenerated esophagus. Microscopically, no foreign material remained at the reconstructed site 1 month after surgery; the collagen sponge was absorbed and replaced by host tissue. Complete epithelization was observed within 3 months. Regeneration of the lamina muscularis mucosae, esophageal glands, and skeletal muscle were observed near the anastomoses. Our artificial esophagus holds promise for esophageal reconstruction in a clinical setting, even in the thorax.
Animals↗
Use of a newly developed artificial nerve conduit to assist peripheral nerve regeneration across a long gap in dogs.
There is now considerable evidence that peripheral nerves have the potential to regenerate if an appropriate microenvironment is provided. However, there are only a few reports of the successful use of artificial nerve conduits to repair major nerve defects more than 30 mm in length. In this study, we examined nerve regeneration across a long gap in the dog peroneal nerve using a novel artificial nerve conduit developed by our group. The conduit consists of a polyglycolic acid (PGA) collagen tube filled with laminin coated collagen fibers. In 12 dogs, the nerve conduit was implanted across an 80 mm gap in the left peroneal nerve. Three months after surgery, compound muscle action potentials (CMAPs) and somatosensory evoked potentials (SEPs) were detected. Evaluation of locomotor function revealed obvious limping for up to 3 months, but no marked difficulty in walking by 6 months. Microscopic observation of the regenerated nerve segment at 12 months showed numerous myelinated nerve fibers, which were smaller in diameter and enclosed in a thinner myelin sheath than normal axons. These results suggest that our artificial nerve conduit has potential usefulness in enhancing peripheral nerve regeneration, even across large gaps.
Action Potentials↗