Whether xenotransplantation of trachea is possible by means of the graft treated with protease or not is the question to be solved in this study.
Pig trachea was used for xenograft. The graft was treated with 75% alcohol for 3 days, 10% hydrogen peroxide for 3 days, protease for 7 days and 0.5% glutaraldehyde for 3 days successively. Thereafter, each graft was sunk into silicon solution in which brittle graft was reinforced again (Fig 1). For protease, 0.05% Papain, 0.05% Ficin, and Varidase including 10, 000units/ml Streptokinase and 2, 500units/ml Streptodornase was used severally. Following biological and immunological tests were measured in the extract of thus treated grafts. Normal untreated pig trachea was used as control. 1) Protein content measurement by Lowryo's method, 2) Polysaccarides measurements --Glucose by Anthrone's method, Glucosamine by Elson-Morgan's method, 3) Passive hemagglutnation activity by SRBC, and 4) Delayed type hypersensitivity reaction (DTH).
Protein content in the trachea treated with each protease was remarkablly lower than normal trachea (Tab. 1). Similarly, Glucose in the treated trachea was significantly lower than normal, and Glucosamine in the graft treated with Papain and Varidase was also lower than normal. Thus, the antigenicity in the pig trachea was suspected to be decreased significantly by means of protease treatments, especially by Papain and Varidase. Humoral antibody response of the treated graft was lower than normal both in IgM and IgG (Tab. 3). DTH reaction showed that cell mediated immunity of the graft treated with Papain is lower than normal (Tab. 4).
In conclusion, above described treatments decreased the antigenicity of the grafts. Furthermore, xenotransplantation of the trachea is possible immunologically.

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Fifteen dogs' cervical, trachea were reconstructed using collagen-plastics copolymer mesh. 4 cases were tracheal patch graft. 2 cases of the 4 were used collagen-silicone mesh. The others were used collagen-polypropyrene mesh. Whole interluminal surface of the mesh of the latter cases were covered with ciliated epithelium. 11 cases of 15 were circumferentiallreconstruction. Central granulomatous stenosis were ensued in 4 cases of the 11. Complete epithelization was obtained by using collagen-polypropyrene mesh with imnlantaion of the cartilagenous pedicles.

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As a simple screening, various biomedical polymers were evaluated their tissue affinity by using the growth rate of fibroblasts upon them. Among control groups, tissue affinity were Ny66 PVC PE PVA. The affinity of Col. SCE II was higher than all of them. Comparing with the affnity of Col-SCE II copolymers treated by various ways, that of r-Ray treated and UV treated groups were as high as simply coated Col-SCE II, but GA treated group was very low or not affinitive.

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Based upon the standpoint that we might expect to tailor natural materials selectively and to introduce new properties by chemical treatments, regeneration of the peritoneum was studied using aceton pretreated acethylated and methyl-acethylatedbovine pericardium as substitutional materials in rabbits.
Complete regeneration of the defected peritoneums were noted after 6 months transplantaion in the both series and no disorders of the Gastro-intestinal tracts were seen during the entire experimental period.

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To evaluate biocompatibility of polyurethanes (PU), 2 room-temperature cure medical grade PU used in hollow fiber artificial kidney as sealant and 7 general grade thermoplastic PU (4 polyether type, 2 polyester type and 1 polycaprolactone type) were tested by our in vitro evaluation program, which consists of repeated extraction test, hemolysis test and tissue culture test. Three different types of PU were also implanted in rats for 1 to 12 weeks for histopathological evaluation. Room-temperature cure PU seemed the most biocompatible and the results were considerably different from one another among thermoplastic PU.

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Eight medical grade poly (vinyl chloride) (PVC) used mainly in hemodialysis were evaluated and compared with medical grade silicone rubber by our in vitro test program, which consists of repeated extraction test, hemolysis test and tissue culture test. PVC materials were more hemolytic, more hemoglobin denaturative and more inhibitive of cell growth than silicone rubber. The results were considerably different from one another among the PVC materials tested. Two PVC seemed comparatively safer than the others. It is recommended to select and to use safer materials among the PVC products available.

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A new histological method of estimating the in vivo performance of biomedical polymer materials was developed by means of microspheres. Some kinds of microsphere suspensions in saline were injected noninvasively into the target organs e. g. muscle, liver, kidney, pancreas and spleen of rats. The bioreactions of the injected regions were histologically examined. In addition, the microspheres coated with a variety of polyelectrolyte complexes under development were injected and the bioreactivity of the coated materials was evaluated. The microsphere method was found to be very advantageous as compared with the conventional method e. g. the filmimplantation method.

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Mouse peritoneal macrophages were reacted with gutta percha, a kind of natural rubber which widely used as the root cannal filling materials in endodontic therapy. Fine gutta percha particles were phagocytized by mouse macrophages in vitro. Intraperitoneally injected gutta percha particles stimulated peritoneal macrophages and accumulated in milky spot on the omentum. Intraperitoneally implanted pure gutta percha membranes were covered and penetrated by macrophages. Clinically used gutta percha membranes were digested partialy in the same enviroment. Thus, the evidence has been obtained that gutta percha is not biologically inert in strict sense, but induce the defence reactions in the doby.

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Polyvinylalcohol (PVA) was used for microencapsulation of beaded activated charcoal. Encapsulated charcoal was immersed in heparin solution to provide the capsule with anticoagulability. PVA proved to be a suitable material for microcapsulation. The capsule was found smooth by scanning electron microscope and did not reduce adsorptive capability of the activated charcoal, however effects of heparin incorporation could not be manifested by in vitro study using human blood as well as in extracorporial circulation using dogs.

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Coimmobilizing antithrombin III and heparin (I-AT III·Hep.) to the surfaces of biomedical materials by the method of covalent linkage, the synergetic effect of the AT III and Hep. on antithrombin activity was observed. I-AT III·Hep. showed the rapid and powerful anticoagulative activity than I-Hep. reported previously. (1, 2) In the plasma recalcification test, I-AT III·Hep. had the excellent synergetic effect of AT III and Hep. on anticoagulative reaction. The anticoagulative activity of I-AT III·Hep. was much higher than that of I-AT III which was obtained by immobilizing AT III under the addition of acetylated Hep.. Using Sep. 4B, P. V. A. and Poly HEMA as biomedical materials, the same anticoagulative results were obtained. The antithrombin activity of I-AT III·Hep. could be regenerated with eluation by 1M sodium acetate and no decrease of antithrombin activity was entirely observed after the regenerations of 10 times. These biomedical materials with immobilized AT III and Hep. were very stable, and AT III and Hep. did not break out for a storage of 5 months.

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Arteriovenous shunt method using newly developed “Flow Cell” has been used to evaluate thromboresistance of the materials containing heparinized hydrophilic polymers. The effect of both shear rate and contact surface area of blood and the test materials on the thrombus formation was studied. Heparinized hydrophilic polymers were found to be markedly thromboresistant in the region of larger contact surface area and lower shear rate comparing with silicone rubber and polyurethane. Scanning electron microscopic studies also showed only undeformed platelet adhesion onto the surface of heparinized hydrophilic polymers.

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Antithrombogenic catheter coated with heparinized hydrophilic polymer (H-RSD) has been developed. After the experiments in animals, this catheter has been used in patients as the indwelling catheter in the central vein for transfusion or hyperalimentation. Thrombus formation due to the catheters were examined clinically by pullout venography, and by scanning electromicroscopy of the surface of these catheters after removal from the patients. Thrombus formation due to the catheter made of polyvinyl chrolide, polyethylen, and compared with results in H-RSD catheters. Fibrin sleeve fomation and the thrombus of the venous wall was much less than other catheters. We also found that thrombus in and around the catheters could be a good media for the growth of microorganisms.

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Collagen-coated synthetic polymer, a biomaterial which possesses high tissue compatibility, has been shown to be adequately applicable for a support of the immobilization of trypsin and urokinase. The enzymes were successfully bound to the collagen membrane activated by acyl azide formation from its carboxyl groups. The urokinase-bearing collagen-coated synthetic polymer showed fibrinolytic activity on fibrin-agarose plate. Thus, the enzyme immobilized onto the surface of collagen provides the material with some biological functions. In view of high plasticity of synthetic polymers, an enzyme-collagen-polymer complex will find wide applications for biomaterials and artificial organs.

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This report was investigated to establish the more effective immobilization method which was able to produce the stronger fibrinolytic activity in nylon immobilized urokinase.
For this purpose, we designed five procedures that urokinase was immobilized to nylon (1) without any treatment, (2) after the etching of 3N HCI (3) through the grafted copolymer such as polyethy leneimine and (3) gantrez, and (5) under the combination of linking of nitrophthalic acid. The relative merits of these each procedures were examined on a view-point of the intensity of fibrinolytic activity the stability of repeated fibrinolysis and the influence of disinfection.
From these experiments, the available immobiliza tion methods were the procedures of N/PEI/G/UK and N/PEI/G: NP/UK.

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Urokinase (UK), a plasminogen activator was immobilized on nylon and silicone surfaces by application of a newly devised technique. These new preparations showed stable activity in vitro. Thrombus formation time (TFT) of these tubes was remarkably longer than that of other materials. When applied clinically, the UK-immobilized tubes proved to have excellent thromboresistance.
The newly devised preparations showed a great promise for application as antithrombogenic materials.

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A new antithrombogenic elastomer (H-USD) has been developed by heparinizing the blend polymer (USD⁺) composed of segmented polyurethane (U) and cationic hydrophilic crosslinkable terpolymer (SD⁺).
The relationship between higher order structure of USD⁺ or H-USD and their antithrombogenicity was studied. Moderate phase separation of blend polymer was found to be necessary for antithrombogenicity owing to their effective heparin absorption and elution.
The degree of phase separation was controlled by changing the blend ratio of U and SD⁺, then the optimum blend ratio for both antithrombogenicity and mechanical strength was determined.

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Membrane lung has been studied for more than ten years in our clinic. Major projects were design of membrane lung and extracorporeal circulation system with membrane lung.
This time, however, effect of extracorporeal circulation on blood and patients was compared between types of artificial lung: membrane lung, bubble oxygenator and disc oxygenator.
Serum LDH, total bilirubin, serum protein and its fraction were studied pre and postoperatively. Postoperative courses were carefully observed.
From postoperative change of these parameters, following considerations were induced. Superiority of membrane lung to bubble oxygenator (Temptrol) was not confirmed by only these parameters. But it is recognized that membrane lung and Temptrol oxygenator are far better than the disc oxygenator.
Our newly designed, automatically controlled bypass circuit with membrane lung was introduced together in this paper.

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Since 1972, we have been used Membrane Oxygenator for open heart surgery. Recentry 500 cases, Kolobow Spiral Coil Membrane Oxgenator have been used. 0.8sq.M. oxygenator was used in 58 cases, 1.5sq.M. in 117 cases, 2.5sq.M. in 65 cases, 3.5sq.M. in 233 cases and 4.5sq.M. in 27 cases. Max, blood flow of each oxygenator was 600ml/min. at 0.8sq.M. lung, 1.51/min. at 1.5sq.M., 2.51/min. at 2.5sq.M., 4.01/min. at 3.5sq.M., and 5.51/min. at 4.5sq.M.. And rated gas flow was 1.0-2.0 of V/Q. and 50% of FiO₂.

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Although the membrane oxygenator has been recognized as the ideal artificial lung, the use of it is not popular as should be, because of insufficient oxygen transfer rate, difficult assembly, high experase and leakage.
In this point of view, we have attempted to make many changes for improvement for over the last 10 years.
Our most recent model is a parallel plate type membrane oxygenator, which is small in size, simple in design, casy to handle and capable to mass production. The in vitro and vivo evaluation proved that this oxygenator had excellent gas transfer characteristics.

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Silicone rubber has found wide application of membrane oxygenator on the high gas transfer properties. Pure silicone rubber has a rather low tensile strength which must be increased by the additional of filler materials, silica, in order to be utilized. The new coil membrane oxygenator has conposited of membranes which the oxygen layer consists of standard silicone rubber and the blood contacting layer consists of filler-free silicone rubber. This membrane well suited for use in a new coil membrane oxygenator, and this study was undertaken to evaluate the O2 and CO2 transfer of a new oxygenator.

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One of the attractive ways to design compact oxygenators with high gas transfer performance, is to weave tubings tightly. This gives basically two advantages: the augmentation of gas transfer due to curved tube and larger packing density of tubes. In this study gas transfer performances in water and blood were investigated experimentally for prototype units having four single tubes wound in two kinds of weaving patterns. The augmentation effects similar to that of helical coils were obtained for both units, however, the flow resistance in the blood path turned out to be half that of helical coils.

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Rates of Oxygen absorption into blood and carbon dioxide desorption from blood were measured in flat plate membrane oxygenators with and without turbulence promoting screens between membranes. In the oxygenators with screens rates of gas transfer were increased due to reduction of the blood phase resistance. Rates of carbon dioxide transfer were sufficient in comparison with the rates of oxygen transfer.

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