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Biomedical subjects

S Hitomi

Publications and source records attributed to S Hitomi.

At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

Pancreatic insulo-acinar portal systems in humans, rats, and some other mammals: scanning electron microscopy of vascular casts.

Scanning electron microscopy of vascular casts showed that in the mouse, rat, and guinea pig, the pancreatic endocrine islets were frequently interlobular in position and emitted insulo-venous efferent vessels directly draining into veins. In these animals, the intralobular islets, located within the exocrine lobules, issued insulo-acinar portal vessels continuous with the lobular capillaries in addition to the insulo-venous efferent vessels. In humans, monkeys, cows, pigs, dogs, cats, and rabbits, essentially all islets in the pancreas were intralobular in location and emitted the insulo-acinar portal vessels only. In man and animals examined, especially in the murine species, many lobules lacked an islet, therefore the insular control over the exocrine pancreas seemed to be effected in more or less restricted areas of lobules.

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PubMedDate not supplied

Experimental studies on an artificial esophagus for the purpose of neoesophageal epithelization using a collagen-coated silicone tube.

An artificial esophagus was fabricated from a collagen-coated silicone tube 5 cm long, with an inner diameter of 2.5 cm and a wall thickness of 1 mm. The outer surface was coated with dry collagen to 5 mm thickness. The bilayered prosthesis was anastomosed to the cervical esophagus of adult mongrel dogs that were fed only by intravenous hyperalimentation (IVH) with 80 cal/kg/day and 60 ml water/kg/day for 3 weeks after the operation. Once the dogs began to consume food orally, the artificial esophagus dropped spontaneously into the stomach and formation of the neoesophagus was complete. Macroscopically, the neoesophagus showed no evidence of leakage or inflammation and had a smooth internal surface, but it developed slight segmental narrowing. Microscopically, layers of stratified squamous epithelium covered the neoesophagus within 3 to 4 weeks. The most characteristic feature of the artificial esophagus was that the replacement prosthesis did not remain in the esophagus after healing. Esophageal epithelization extended into the collagen layer coating the silicone tube and a new esophageal lumen was regenerated, thereby decreasing the chance of infection and leakage. However, neoesophageal stenosis was observed when the silicone tube was removed.

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PubMedDate not supplied

Experimental studies on an artificial trachea of collagen-coated poly(L-lactic acid) mesh or unwoven cloth combined with a periosteal graft.

Artificial tracheas were fabricated from poly(L-lactic acid) mesh or unwoven cloth coated with collagen in order to reconstruct the respiratory airway by self regeneration without retaining the prosthesis at the replacement site, thus preventing infection, air leakage, granulation tissue formation, and displacement of the prosthesis. Nine weeks after placing a periosteal autologous graft from the tibia around the cervical trachea of a rabbit, bone rings formed without infection. Two weeks after replacement of an 8 X 8 mm window-shaped section of the cervical trachea with autologous periosteum, the internal surface of the trachea was well epithelialized without local complications, but ossification was not seen. One week after cervical substitution with our 2 cm long artificial trachea combined with the periosteal graft, cartilage was produced around the mesh material but neither ossification nor epithelization was observed thereafter, probably due to local infection. On the other hand, cartilage, bone, and epithelium did not form around the unwoven cloth artificial trachea after the substitution, probably because of severe infection due to collapse of the tracheal lumen. However, the formation of bone rings around the trachea suggests preservation of the neotracheal lumen, which may have potential for the treatment of tracheomalacia and/or bronchomalacia.

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PubMedDate not supplied

Experimental application of polyvinyl alcohol-silica for small artificial vessels.

Polyvinyl alcohol-silica (PVA-SiO2) composite and heparinized PVA-SiO2 were examined in vitro and in vivo as materials to coat artificial vessels to be used for the replacement of small arteries. PVA-SiO2 was observed to prolong coagulation time and on heparinized PVA-SiO2 surfaces no blood coagulation was noticed after a period of two days using the Lee-White and plasma recalcification methods. After placing non-coated and coated surfaces in contact with blood components in vitro and in vivo, the degree of blood component adhesion was greater in non-coated woven Dacron than in PVA-SiO2 coated Dacron. The degree of adhesion was even less in heparinized PVA-SiO2 coated Dacron. Furthermore, artificial vessels made of these 3 types of materials were used to replace parts of the canine abdominal aorta and were removed one and a half years later. Patency rates were as follows: non-coated 2/7, PVA-SiO2-coated 4/7, heparinized PVA-SiO2-coated 8/12. The inner surfaces of these prostheses were observed with light microscopy and scanning electron microscopy. Intima formation was thinner on the PVA-SiO2 composite surfaces than on the control surfaces. Heparin acted as a local anticoagulant and PVA-SiO2 limited intima formation. This report showed that PVA-SiO2 composite coated surfaces can be effective for small artery replacement due to good tissue affinity and anticoagulability.

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