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Biomedical subjects

Y Ikada

Publications and source records attributed to Y Ikada.

At least 289 records · Page 16Linked to original sources
PubMed1981

Blood compatibility of hydrophilic polymers.

Blood compatibility has been studied for hydrophilic polymers such as poly(vinyl alcohol) (PVA), its derivative, and polyethylene grafted with water-soluble monomers. The surfaces in contact with electrolyte solutions have been characterized by measuring the zeta potentials. The study of plasma protein adsorption on these polymers has revealed that bovine serum albumin as well as bovine serum fibrinogen adsorbs to a lesser extent as the hydrophilicity of the polymers increases. Platelet deposition and fibrin formation, examined using platelet-rich plasma, have been found to take place less significantly on PVA as well as sodium acrylate- and acrylamide-grafted polyethylene than on nongrafted and acrylic acid-grafted polyethylene. Ex vivo experiments with canine whole blood have shown that formation of thrombus on PVA is less than on siliconized glass but increases upon heat treatment which reduces the hydrophilicity. When PVA tubes of about 1 mm diameter are anastomosed to the carotid artery of rat, the patency rate is found to depend strongly on the anastomotic technique. From the results on the zeta potential and the experiments in vitro and ex vivo it can be concluded that the material having a surface from which solvated, neutral chains are extended into the outer aqueous phase may exhibit excellent resistance to thrombus formation.

Adsorption↗
PubMed1980

Radiopaque solidifying liquids for releasable balloon technique: a technical note.

Recently we have reported a catheter having a balloon which can be released simply by twisting the catheter. In the technique, 2-hydroxyethylmethacrylate (HEMA) has been used as a solidifying liquid to prevent the released balloon from deflating. Since HEMA is not radiopaque, the place and the size of the balloon cannot be visualized under an X-ray image intensifier. The present investigation involves the preparation of a radiopaque, solidifying liquid, by mixing HEMA with a suitable contrast medium such as metrizamide, sodium iothalamate or meglumine sodium iodamide. The use of HEMA-contrast medium mixtures made injection of the solidifying liquids much more controllable.

Acrylic Resins↗
PubMed1980

The releasable balloon technique with activated high frequency electrical current.

A new releasable balloon catheter was developed which has a soluble joint connecting the balloon and the catheter. The joint is made from a polyvinyl alcohol tube and has two electrodes. When a high frequency electrical current is activated, the resulting heat causes the joint to disappear within one second. The type of generator used in the experiment was an Aesculap GK-34. This catheter was used for embolization of carotid-jugular fistulas in dogs.

Animals↗
PubMed1979

Grafting of proteins onto polymer surfaces with the use of oxidized starch.

A study has been carried out on the coupling of proteins onto crosslinked poly(vinyl alcohol) hydrogel membranes and ethylene-vinyl alcohol copolymer(EVA) films previously grafted with oxidized starches having many pendant aldehyde groups. The coupling reaction of proteins is based on the Schiff's base formation between the amino groups of proteins and the aldehyde groups of the oxidized starches which have been grafted onto the substrate membrane or film through acetalization of the aldehyde of starch with hydroxyl groups of the substrate polymers. The grafting of oxidized starches onto the EVA films seems to be restricted to the film surface, since no detectable change is observed in the weight and the attenuated total reflection infrared spectrum of the grafted films. The amount of grafted protein, determined by the ninhydrin method, reveals that, at least, plasma proteins such as serum albumin and fibrinogen are grafted to the film surface in a monomolecular layer without undergoing a marked denaturation. The alpha-amylase grafted onto the EVA film showed a distinct enzymatic activity in hydrolysis of amylose and starch, but the activity was very low compared with that of the ungrafted, soluble alpha-amylase.

Adsorption↗
PubMed1979

Embolization and superselective angiography by means of balloon catheters.

Three types of thin flexible balloon catheters were made. One of them is a releasable balloon catheter, which is prepared for embolization of intracranial aneurysms, arteriovenous malformations and fistulas. The other two are nonreleasable balloon catheters that are utilized for temporary occlusion, catheterization, and superselective angiography of the intracranial arteries. These catheters are useful experimentally for the above mentioned purposes. Our clinical experiences with catheterization and superselective angiography with our balloon catheter are reported.

Animals↗
PubMed1979

Balloon embolization of a giant aneurysm using a newly developed catheter.

A new catheter with a releasable balloon has been developed for the controllable embolization of intracranial vascular lesions located beyond many arterial curves such as the carotid siphon. Embolization is accomplished by introduction of the balloon to the lesion, followed by inflating the balloon with a polymerizable liquid. After this liquid sets to a gel, the catheter is twisted off to detach the balloon at a specially designed joint. This balloon catheter has been used clinically to embolize an aneurysm of the middle cerebral artery.

Aged↗
PubMed1979

[Nonsuture microvascular anastomosis--experimental arterial end-to-end anastomosis using plastic adhesive and a soluble PVA tube (author's transl)].

Microvascular anastomosis is now widely applied and many improved methods of the nonsuture anastomosis have been developed instead of the suture anastomosis for the purpose of saving time and making the reconstruction easier. We introduced a new nonsuture method of microvascular anastomosis using plastic adhesive and a soluble tube made of polyvinylalcohol (PVA). PVA, which had been utilized as a plasma expander, is a water-soluble polymer and its solubility is changeable depending on the degree of polimerization and percent saponification. We have made two kinds of soluble PVA tubes, the one has monolayer wall and the other double layered wall. The inner wall of the latter is more soluble than the outer wall. As plastic adhesives, we employed ethyl 2--cyanoacrylate, isopropyl 2--cyanoacrylate, and isobutyl 2--cyanoacrylate which were much superior to methyl 2--cyanoacrylate. Common carotid arteries of rats of 1.0 to 1.3 mm external diameter range were reconstructed and re-exploration was carried out at intervals of more than 7 days after operation. The anastomotic technique was very easy and it took about five minutes to reconstruct. In our last series, approximately 98 percent patency rate was achieved. The advantage of our method is that the blood stream is regained in the small soluble at the anastomotic site immediately after the release of hemostatic clamps.

Animals↗
PubMedDate not supplied

Experimental nonsuture microvascular anastomosis using a soluble PVA tube and plastic adhesive.

This article describes a new nonsuture method for microvascular anastomoses that uses plastic adhesives and soluble tube stents made of polyvinyl alcohol (PVA). Three soluble tubes were studied: one tube with a monolayered wall and two bilayered tubes of different thicknesses. The layers of the bilayered tubes consisted of PVA of different degrees of solubility. As plastic adhesives, ethyl 2-cyanoacrylate, isopropyl 2-cyanoacrylate, isobutyl 2-cyanoacrylate, and methyl 2-cyanoacrylate were employed; methyl 2-cyanoacrylate was by far the least effective. Anastomoses were performed on the common carotid artery of rats, and macroscopic, angiographic, and histologic investigations were carried out at intervals ranging from seven days to six months. The patency rates were 81% for the monolayered tube, and 92% and 98% for the bilayered tubes. The principal advantage of this method is that blood flow can be reestablished through the anastomosed site immediately after release of the hemostatic clamps.

Adhesives↗
PubMedDate not supplied

Experimental embolization of rabbit renal arteries to compare the effects of poly L-lactic acid microspheres with and without epirubicin release against intraarterial injection of epirubicin.

PURPOSE: We performed a basic investigation using white rabbits of the sustained release and embolizing effects of poly L-lactic acid microspheres (PLA) to determine their usefulness for chemoembolization. METHODS: Fifteen male Japanese white rabbits were used. Sustained release of an embolizing material, EPI-PLA was accomplished with 1 mg of PLA containing 0.03 mg of epirubicin hydrochloride (EPI). Embolization with 50 mg of PLA (total dose of EPI 1.5 mg) was performed after the renal artery of the rabbits was selected (Chemo-TAE group). A group in which a bolus of 1.5 mg EPI alone was injected through the renal artery (TAI group) was established as a control group. Furthermore, a group in which embolization was performed with 50 mg of PLA alone (TAE group) was also established. These three groups, each consisting of five rabbits, were compared. RESULTS: Blood EPI levels were serially measured. The blood EPI level in the TAI group rapidly reached a peak more than 30 min after injection, then decreased to almost zero 24 hr after injection. In the Chemo-TAE group, the blood EPI level was transiently increased 30 min after embolization, but remained low thereafter until 24 hr after embolization. EPI levels in kidney tissue isolated 24 hr after embolization were measured. In the Chemo-TAE group, the tissue EPI level was significantly higher than that in the TAI group. When isolated kidneys were macroscopically and histologically examined, atrophy of the entire embolized kidney, as well as infarction and necrosis in the renal cortex, were observed in both the TAE group and the Chemo-TAE group. However, there were no such findings in the TAI group. The area of the infarction in the renal cortex did not significantly differ between the Chemo-TAE group and the TAE group; however, there was vascular injury in the Chemo-TAE group and none in the TAE group. CONCLUSION: It was demonstrated that EPI-PLA, a chemoembolizing material, maintained high local concentrations of the anticancer drug, while maintaining low blood levels of the anticancer drug.

Animals↗
PubMedDate not supplied

A bilayer "artificial skin" capable of sustained release of an antibiotic.

The most frequent complication of the bilayer "artificial skin", composed of a silicone sheet and collagen sponge described in a previous paper, was infection beneath it. This paper describes a new type of "artificial skin" in which microspheres containing antibiotics were installed beneath the silicone sheet, allowing a continuous release of antibiotics.

Adult↗
PubMedDate not supplied

A newly developed three-layer agarose microcapsule for a promising biohybrid artificial pancreas: rat to mouse xenotransplantation.

We examined the effectiveness of an improved version of a three-layer agarose microcapsule in islet xenotransplantation. The microcapsule is composed of a mixture of 5% agarose and 5% polystyrene sulfonic acid. The other two outer layers are polybrene and carboxymethyl cellulose. The agarose/polystyrene sulfonic acid membrane is for the purpose of immunoisolation, suppression of complement activity and reinforcement of the microcapsule. The polybrene layer suppresses the polystyrene sulfonic acid leakage by forming a polyionic complex at the surface of the agarose/polystyrene sulfonic acid membrane. The outermost layer, a carboxymethyl cellulose coating, improves the biocompatibility of the microcapsule. In vitro static incubation study showed that the insulin secretion from rat islets in microcapsules in response to 16.7 mM glucose stimulation was more than four times higher than that on 3.3 mM glucose stimulation (n = 8). In an in vivo study, 500 rat islets in microcapsules were xenogenically implanted in the abdominal cavity of mice with streptozotocin-induced diabetes. The graft survival times ranged from 2 to 5 mo, the average being 75 days (n = 5). Our results demonstrate that the improved version of the three-layer agarose microcapsule can effectively prolong the xenograft survival time without employing immunosuppressants, suggesting that this microcapsule could provide a promising biohybrid artificial pancreas for future clinical applications.

Animals↗