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Biomedical subjects

Y Ikada

Publications and source records attributed to Y Ikada.

316 records · Page 18Linked to original sources
PubMedDate not supplied

Improved large-scale isolation of breeder porcine islets: possibility of harvesting from nonheart-beating donor.

To establish a large-scale isolation procedure for adult porcine islets usable as a donor source for xenotransplantation and as a model of human islet isolation, we improved several characteristics of the conventional isolation procedure. At a slaughterhouse we first selected a breeder pig over 1.5 years old (and over 200 kg in weight) with warm ischemic time (WIT) of 15 +/- 2 minutes as nonheart-beating donors. Then, we made a special enzymic mixture that consisted of collagenase S-1 (260 U/mg, NittaZelatin, Japan), collagenase P (1.86 U/ml Lyo Boehringer-Mannheim, USA), DNase (Sigma, St. Louis, Mo), Disparse (NittaZelatin, Japan), and protease inhibitor (Sigma). Third, this mixture was injected very gently into the pancreatic duct at the time of pancreatic harvesting. To prevent overdigestion of the pancreas, the mixture was first cooled to less than 10 degrees C. Fourth, during the warm digestion of pancreas, the pancreas with the enzymic mixture was quietly put in a water bath at 37 degrees C without mechanical shaking. Fifth, we purified the islets with a COBE 2991 cell processor by the Dextran 70 gradient method, because Dextran 70 is very cheap and has the same purification effect as the Ficoll gradient. The results of 10 consecutive breeder porcine islet isolations are reported. The total yield of isolations of islets over 50 microm in the longest diameter after staining with Dithizone (DTZ) was 85,900 +/- 19,954 islets, 291,667 +/- 240,452 IEQ (2,900 +/- 2,324 IEQ/g). The purity of the isolated islets was very high: 90.2 +/- 3.8%. Glucose stimulation during in vitro incubation induced significant insulin release from isolated breeder porcine islets. In two of the diabetic rats receiving encapsulated islets grafts using a mesh-reinforced polyvinyl alcohol hydrogel bag (MRPB), a prominent reduction in serum glucose levels (less than 200 mg/dL) persisted for 13 and 19 days, respectively, after intraperitoneal xenotransplantation islets without immunosuppression. In conclusion, we succeeded in a more efficient and less-expensive isolation of a large amount of adult porcine islets from a nonheart-beating donor.

Animals↗
PubMedDate not supplied

Novel method for isolation of adult porcine pancreatic islets with two-stage digestion procedure.

It is particularly difficult to isolate porcine islets (PI). Experience suggests that the success rate of porcine islet isolation (PII) is probably considerably influenced by the distension and digestion of the pancreas. In this study, we divided the digestion procedure into two stages and developed a new enzyme solution to improve both the distension and digestion procedures. As a result, we established a novel and stable method of large-scale adult porcine islet isolation (APII). The harvested pancreata of 2-year-old pigs weighing over 200 kg (n = 18) were distended by introducing our new enzyme solution gently and slowly through the pancreatic ducts. Two-stage digestion (cold, then warm) was then performed by first placing the distended pancreata on ice for 2 h to cause diffusion of the enzyme solution around the islets, and then by incubating the pancreata in a water bath at 37 degrees C for 45 min without shaking. The islets were purified by a COBE 2991 cell processor on dextran T70 discontinuous density gradients. Histological study was performed on porcine pancreata sampled after 0, 15, 30, and 45 min of the second stage, and stained with H&E stain. Next, islet equivalent was calculated. Static incubation study was performed by stimulating the islets with 3.3 and 16.7 mM glucose in Krebs' Ringer bicarbonate buffer (KRBB) solution at 37 degrees C for 1 h, and finally the insulin released was measured. The dilated acinar cells septa around the islets were observed at time 0. Destruction of the acinar cells around the islets by warm digestion was recognized at 15 and 30 min, and destroyed and separated acinar cells present around the islets at 45 min. During the entire course of the warm digestion, the islets remained intact. The number of isolated islets was 291,667 +/- 240,452 IEQ/pancreas (n = 14) and 3,294 +/- 2199 IEQ/g of pancreatic tissue. The purity of recovered porcine islets was over 90%. The concentration of the insulin secreted by 10,000 IEQ islets selected at random was 83.9 +/- 13.4 microU/dish/h in response to 3.3 mM glucose and 104.1 +/- 12.9 microU/dish/h in response to 16.7 mM glucose (n = 20). A success rate of approximately 80% was attained with APII. We demonstrated that this increase in the success rate was due to the improved distension and digestion provided by this method. This two-stage APII method with its new enzyme solution may facilitate the future use of porcine islets in clinical xenotransplantation trials.

Animals↗
PubMedDate not supplied

Experimental study of a new tracheal prosthesis made from collagen-grafted mesh.

The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex mesh reinforced with a continuous Teflon spiral, and it is grafted and coated with pig collagen, with the aim of promoting connective tissue infiltration and providing air-tightness during the initial stage of implantation. Complete surgical resection and replacement of a 4-6 tracheal ring segment of the cervical trachea was performed in 13 adult mongrel dogs. Except for two dogs that developed anastomotic insufficiency, the prostheses in all dogs were infiltrated by the surrounding connective tissue, and were completely incorporated by the host trachea at the anastomotic sites. Formation of respiratory epithelium that lined the prosthesis lumen, was seen to varying degrees, and in one dog killed at 4 months after reconstruction, this was confirmed histologically from the upper to the lower anastomosis of the prosthesis. Stenosis of the lumen often occurred, however, due to deformation of the prosthesis and overgrowth of granulation tissue. The authors conclude that this tracheal prosthesis is highly biocompatible, and might be useful for repairing tracheal defects by improving prosthesis processing, especially that used for insertion of stents.

Animals↗
PubMedDate not supplied

Experimental studies of a hybrid artificial esophagus combined with autologous mucosal cells.

Preliminary results, obtained using an artificial esophagus combined with autologous mucosal cells in dogs, are reported. The authors' prosthesis is a silicone tube coated with freeze dried collagen sponge. Cells infiltrate this collagen layer and synthesize new tissue, which will become the neoesophagus. The silicone tube imparts rigidity to the prosthesis and prevents infection, leakage, and dislocation of the prosthesis at the anastomotic site. After formation of the epithelized neoesophageal lumen, the silicone tube drops into the stomach as the result of peristalsis in response to food. Eventually, no artificial prosthesis remains in place, and the defect is replaced by ingrowing tissue. This process was shortened by mucosal cell seeding. Before replacement, the authors harvested oral mucosal (OM) cells, cultured them for 10 days, and seeded them in the collagen layer of the prosthesis just after anastomosis. The neo-esophageal lumen was formed 1 week after the operation without any local complications, infection, leakage, or stenosis, and 2 weeks later the firm, epithelized neoesophagus was completed. OM cell seeding accelerated not only epithelization, but also regeneration of mesenchymal tissue. Parallel with this, transmission electron microscopy showed that most of the cells in the neoesophagus exhibited large nuclei and prominent rough endoplasmic reticulum, indicative of active collagen production.

Animals↗
PubMedDate not supplied

Clinical effects of a polyethylene glycol grafted cellulose membrane on thrombogenicity and biocompatibility during hemodialysis.

The biocompatibility and thrombogenicity of polyethylene-glycol (PEG)-grafted cellulose hemodialysis (HD) membranes (PEGC) were investigated in cross-over HD of five HD patients with ordinary cellulose (OC). The PEGC significantly suppressed transient leukocyte and thrombocytopenia, and release of C3a, beta-thromboglobulin and platelet factor 4, in corresponding with the quantity of grafted PEG. HD with PEGC resulted in lower granulocyte elastase production, protein and blood cells adsorption on the membrane surface than those with OC. Minimum heparin in HD with PEGC was three times lower than that with OC, with the thrombin-antithrombin III complex elevation lower than that in HD with OC. The results indicate that the grafted PEG effectively suppresses blood and membrane interaction, thus improving biocompatibility and reducing thrombogenicity in clinical HD.

Biocompatible Materials↗
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↗
PubMedDate not supplied

Insulin release from a bioartificial pancreas using a mesh reinforced polyvinyl alcohol hydrogel tube. An in vitro study.

Islet transplantation with a bioartificial pancreas is a potential alternative to whole pancreas transplantation. The authors constructed a bioartificial pancreas using mesh reinforced polyvinyl alcohol hydrogel tubes (MRPT), in an attempt to clarify the in vitro responsiveness to glucose of islets seeded in the MRPT. When the MRPT were perfused in a small chamber with buffer containing 3.3 mmol or 16.7 mmol glucose, insulin release from the MRPT began to increase at 9 +/- 3 min, reaching a plateau at approximately 40 min after the glucose concentration in the perfusate increased from 3.3 to 16.7 mmol. When MRPT seeded with islets were subjected to static incubation in buffer containing 3.3 mmol or 16.7 mmol glucose, insulin release from the MRPT remained elevated for 3 hr of high glucose stimulation, the amount of secreted insulin depending upon the number of islets seeded. Although pre incubation of semipermeable membranes in culture medium containing fetal bovine serum prior to seeding with islets has recently been reported to improve insulin release, the authors found that such pre treatment of the MRPT did not have a beneficial effect. Their in vitro findings in this study suggest that the bioartificial pancreas using MRPT could be a promising therapeutic approach to human diabetes mellitus.

Animals↗
PubMedDate not supplied

Treatment of a spontaneous carotid cavernous fistula using an electrodetachable microcoil.

The authors detail their use of a modified version of an electrolysis coil currently manufactured in the United States. They connect a platinum wire to a stainless steel wire via a copper segment, and apply low voltage current to induce thrombosis while electrolysis of the copper effects separation of the platinum coil. Their technique shows potential for treatment of complicated carotid cavernous fistulas.

Arteriovenous Fistula↗
PubMedDate not supplied

Experimental and clinical evaluation of cisplatin-containing microspheres as intraperitoneal chemotherapy for ovarian cancer.

BACKGROUND: We aimed to evaluate the in vitro and in vivo effects of poly [L-lactic acid] microsphere containing cisplatin (CDDP-MS) for intraperitoneal (i.p.) chemotherapy for ovarian cancer. METHODS: We initially examined the in vitro and in vivo profile of cisplatin release from the CDDP-MS, then this drug delivery system was evaluated in 15 patients. RESULTS: The in vitro study showed that cisplatin was released constantly over a 3-week period. Rats in the CDDP-MS group had a significantly lower peak serum concentration of platinum compared with rats in the aqueous cisplatin solution (CDDP-S) group; the serum concentration of platinum showed a gradual decline. The ascitic fluid concentration of platinum also gradually decreased in the CDDP-MS group. We treated 15 patients with recurrent ovarian cancer with CDDP-MS containing 200 mg of cisplatin (n = 5) or CDDP-S containing 100 mg of cisplatin (n = 10) administered i.p. The peak serum and ascites concentrations of platinum were lower immediately after administration of CDDP-MS than after administration of CDDP-S, but increased over time in the CDDP-MS group, reflecting the slow-release effect of CDDP-MS. Grade 1 to 2 leukopenia and/or neutropenia occurred in 2 of 5 patients. No thrombocytopenia or renal or neurologic toxicity was observed; CONCLUSION: These findings indicate that the i.p. administration of CDDP-MS increased the dose intensity of cisplatin and appeared to be safe and effective for the treatment of ovarian cancer.

Adult↗