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Biomedical subjects

Y Takimoto

Publications and source records attributed to Y Takimoto.

At least 127 records · Page 7Linked to original sources
PubMed1976

[Adenoid cystic carcinoma extended to Gasserian ganglion-report of two cases (author's transl)].

Adenoid cystic carcinoma is an uncommon tumor, especially in cases of its extension into the cranial cavity. Two cases of this tumor involving Gasserian ganglion were reported. The first case was a 47 year old female who developed paresis of the right side fifth cranial nerve. The plain skull X-ray of the axial view demonstrated enlargement of the right sided foramen ovale. The tumor was removed exploring the middle fossa extradurally, however its extention through the foramen ovale remained behind. A small induration was found at the base of the oral cavity postoperatively, and the biopsy revealed characteristic findings of adenoid cystic carcinoma histologically. Radiation therapy was followed by considerable clinical improvement.

Adult↗
PubMedDate not supplied

Differential expression of three types of nitric oxide synthase in both infarcted and non-infarcted left ventricles after myocardial infarction in the rat.

In the present report we investigated the differential expression of three types of nitric oxide synthase (NOS) in the left ventricle after myocardial infarction in rats. One, 3, 7, 14, 28 and 56 days (n=6-12 for each group) after ligation of a coronary artery, tissue samples were obtained from infarcted and non-infarcted tissues. The mRNA and protein levels of neuronal (n) NOS, endothelial (e) NOS and inducible (i) NOS were sequentially determined by semi-quantitative reverse transcription-polymerase chain reaction and Western blotting. Progressive left ventricular dilatation and gradual reduction in fractional shortening were confirmed by echocardiography. The expression levels of nNOS were significantly increased 1, 3 and 7 days post-infarct compared to those of sham-operated rats in both the infarcted (P<0.01) and non-infarcted regions (P<0.01). Immunohistochemical analysis showed that nNOS was localized in nerve fibers in the left ventricle and that the number of positive fibers after myocardial infarction had increased compared to that in sham-operated rats. With regard to eNOS, no significant changes in expression levels were detected between infarcted hearts and sham-operated controls. The level of iNOS expression peaked three days post-infarct and then decreased in the infarcted tissue, whereas it increased one day post-infarct, peaked at 14 and 28 days post-infarct and was still elevated in the chronic stage in the ventricular septum. iNOS immunoreactivity was detected in spared cardiomyocytes and macrophages in the infarcted region, and in cardiomyocytes in the ventricular septum. The expressions of three types of NOS were differentially regulated and iNOS produced in the non-infarcted region may contribute to the progression of heart failure after myocardial infarction in rats.

Animals↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

Relationship between stenting time and regeneration of neoesophageal submucosal tissue.

The authors developed a new type of artificial esophagus consisting of an inner silicone tube and an outer non antigenic collagen tube. The novel feature of this artificial esophagus is that the main part of the prosthesis is replaced by host tissue. In a previous study, the authors found that no stenosis of the artificial esophagus developed when the replacement part was stented for more than 4 weeks. It was considered that this stenosis was caused mainly by poor regeneration of submucosal tissue, rather than by the grade of reepithelialization. In this study, it was found that, in cases in which the stent dropped out within 3 weeks, fibrous tissue was noted beneath the neoesophageal epithelium. In such cases, neither muscle layers nor submucosal glands regenerated beneath the neoesophageal epithelium after replacement. However, in cases in which the stent dropped out more than 4 weeks after surgery, the neoesophagus was covered with a polylayer of squamous epithelium and had normal esophageal glands and a muscle layer. Therefore, it was concluded that muscle tissue and esophageal glands were able to regrow in the neoesophagus when the portion replaced by the artificial esophagus was stented for at least 4 weeks.

Animals↗
PubMedDate not supplied

Experimental reconstruction of the intrathoracic trachea using a new prosthesis made from collagen grafted mesh.

Intrathoracic tracheal replacement was performed in dogs using a tracheal prosthesis we had constructed from mesh. The prosthesis consists of Marlex mesh (polypropylene) reinforced with a continuous polypropylene spiral, and is grafted and coated with pig collagen (Types I and III). Complete surgical resection of the mediastinal trachea was performed in seven adult mongrel dogs. In 1 dog, a 4 tracheal ring segment (2 cm) was resected and replaced with a 3 cm prosthesis, and in 6 dogs, a 7 to 8 tracheal ring segment (4 cm) was resected and replaced with a 5 cm prosthesis. In the latter six dogs, a silicone tube was temporarily inserted into the replacement, and removed by bronchoscopy one month after surgery. In one dog that received a 4 cm replacement, we added omentopexy around the reconstructed trachea. The prostheses in all dogs were promptly infiltrated by surrounding tissue and incorporated by the host trachea. No dehiscence or air leakage was observed after surgery. Mild luminal stenosis was evident in one dog, and partial exposure of the mesh (ulceration) was observed in five dogs within an observation period of 3 to 26 months. However, in the dog that received omentopexy after tracheal reconstruction, no stenosis or ulceration was observed, and the luminal surface seemed lustrous even after 6 weeks. Formation of respiratory epithelium, which lined the prosthetic lumen, was seen to various degrees: in the 2 dogs killed 12 months and 26 months after surgery, confluent epithelization was confirmed histologically from the upper to the lower anastomosis of the prosthesis. The tracheal prosthesis is useful for the repair of intrathoracic tracheal defects and shows promise for clinical application with further investigation.

Animals↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

Intrathoracic esophageal replacement with a collagen sponge--silicone double layer tube: evaluation of omental-pedicle wrapping and prolonged placement of an inner stent.

In a previous study, we replaced a 5 cm gap created in the canine intrathoracic esophagus with an artificial esophagus. However, although newly formed esophageal tissue subsequently bridged the gap, mild stenosis occurred, and this seemed to be caused by inadequate regeneration of the skeletal muscle. In the present study, we evaluated whether omental pedicle wrapping (OMPx) of the prosthesis could promote tissue regeneration and whether prolonged retention of the silicone tube within the prosthesis could prevent stenosis. A gap was created in 14 dogs, and the defect was repaired by our prosthesis. OMPx was performed in 5 of the 14 dogs (OMPx group) but not in the rest (control group). The silicone tube was retained for 4 weeks in the control group and for 8 weeks in the OMPx group. All of the dogs in the control group survived for more than 3 months, except for those that were killed. Four dogs in the OMPx group died within 3 months, one caused by perforation at 7 months. Only the thin epithelial and submucosal layer regenerated in the OMPx group. OMPx is not effective for promoting tissue regeneration, and prolonged retention of the silicone tube interrupts epithelial regeneration.

Animals↗
PubMedDate not supplied

Novel airway stent using a thermal shape-memory Ti-Ni alloy.

An attempt was made to develop a tracheal or bronchial stent for nonsurgical implantation using a bronchoscope. Titanium-nickel alloy composed of 50% by weight of each metal has unique thermal shape-memory properties, with a transition temperature of 20 degrees C. Each stent consists of one wire with a diameter of 0.9 mm. It is 30 mm long with a cross-sectional profile resembling a horseshoe. The stent is designed to sustain the airway only at the cartilage rings. Tracheal cartilages of dogs were broken to make a tracheomalasia model, and 10 stents were implanted in 10 animals. The stents were made straight by cooling in liquid nitrogen and then inserted into the region of tracheomalasia. Once in place, they were warmed and recovered their initial shape. The animals were killed between 1 week and 6 months after implantation, and then examined. Nine of the ten stents were located in the implanted area. In one dog, the stent had been displaced into the bifurcation. Microscopic observation showed that the wires were gradually covered with epithelium. At 6 months, 58% were covered with epithelium.

Airway Obstruction↗
PubMedDate not supplied

A new tracheal prosthesis made from collagen grafted mesh.

The authors studied the efficacy of a new tracheal prosthesis made from mesh. The prosthesis, 50 mm long and 18-22 mm in diameter, is made from a Marlex mesh cylinder reinforced with a continuous polypropylene spiral that is grafted and coated with porcine collagen to increase its biocompatibility and provide an airtight seal during the initial implantation stage. Circumferential surgical resection and replacement of a seven to nine ring segment of the cervical trachea was performed in 20 adult mongrel dogs. At the time of surgery, a silicone tube was inserted into the tracheal prosthetic lumen to promote secretory transportation until the prosthesis was covered with host tissue. The silicone tube was removed during fiber bronchoscopy 1 month after surgery. With the exception of the prostheses in 3 dogs that died of unrelated causes, all were infiltrated by connective tissue and incorporated completely by the host. One of these 17 dogs died of suffocation caused by luminal stenosis 2.5 months after surgery, but the others survived until they were killed at more than 6 months. The luminal surfaces of the reconstructed tracheae were covered with respiratory epithelium to varying degrees, and in one dog killed at 22 months after surgery, confluent epithelization throughout the length of the prosthesis was confirmed histologically. In eight dogs, prosthetic luminal stenosis occurred because of overgrowth of granulation tissue, which generally was mild in all but three dogs. The authors conclude that this tracheal prosthesis is highly biocompatible and shows promise for clinical application.

Anastomosis, Surgical↗