Search

Background —Despite recent progress in medical and surgical treatment, acute type B aortic dissection still carries a high mortality rate. We have developed a novel cylindrical balloon catheter for less invasive treatment to block the entry of the dissection and induce thrombotic occlusion of the false lumen. The balloon has the shape of a sheet when deflated but a double-cylinder shape when inflated. Therefore, aortic blood flow is maintained through the cylindrical lumen during balloon inflation. Methods and Results —Six beagle dogs underwent a left thoracotomy at the 6th intercostal space. An acute dissection of 4-cm length was created surgically on the descending aorta. The balloon catheter was inserted through the distal descending aorta and advanced to the entry site. The balloon catheter was inflated for 6 hours. The blood flow in the descending aorta and the position of the balloon was monitored by color Doppler echovasculography. Four dogs were killed humanely on the following day and 2 dogs 10 days after the surgery. The descending aorta was examined macroscopically and microscopically in all dogs. In all dogs, the false lumen was occluded by thrombi. Although no dog had clinical evidence of distal thromboembolism, 2 of the 4 dogs that were killed on the second postoperative day had fresh mural thrombi in the true lumen. Conclusions —The false lumen of the acute type B aortic dissection was effectively occluded by the novel cylindrical balloon catheter in the canine experimental model. The thrombus formation in the true lumen is the problem to be solved.

The aim of this study was to develop a new wound dressing with controlled release of antibiotics only in the presence of infection. In the first experiment using an infected dorsal pouch of rats, exudate containing proteinases from pouches contaminated with Staphylococcus aureus or Pseudomonas aeruginosa showed significantly higher hydrolytic activity toward Boc-Val-Pro-Arg-MCA than that from noninfected wounds. The authors then developed a new type of wound dressing (AGX), a drug delivery system in which gentamicin is bound to polyvinylalcohol hydrogel through an enzymatically degradable peptide linker containing a -(D)-Phe-Pro-Arg-sequence. To investigate in vitro effectiveness, AGX was incubated with exudate from S. aureus infected or P. aeruginosa infected wounds. Gentamicin was selectively released from AGX in the presence of the exudate from S. aureus infected or P. aeruginosa infected wounds, but was not released in the presence of exudate from noninfected wounds. Next, AGX or the polyvinylalcohol hydrogel that served as control was incubated with S. aureus in the presence of human plasma. After 24 hours, S. aureus concentration was markedly lower in the case with AGX than in that with polyvinylalcohol hydrogel. These results indicate that proteinases from wounds infected with S. aureus or P. aeruginosa cleaved the linker and gentamicin was released.

The effects of cold rolling, heat treatment and volume fraction of ferrite on stress corrosion cracking (SCC) behavior of duplex stainless steel have been studied with means of U-bend method in boiling 42% MgCl2 solution. The main results obtained are as follows:(1) SCC susceptibility of the solution treated material is small at about 50% α, but it has a tendency to be increased with either way of increase or decrease of α content from about 50% α. Solution treatment temperature resulting in abrupt increase of SCC susceptibility shifts to higher temperature with the decrease of α content.(2) SCC susceptibility is increased by grain growth of α and γ that occurred with extension of holding time at solution temperature, and otherwise, by cold work in the case of the materials having much volume fraction of α.(3) On aging at 475°C, the hardness is increased by spinodal decomposition of α. The crack resistance increases remarkably with the progress of aging in the case of materials having much α, and corresponds to age hardening behavior.(4) In the case of heating at 700°C, SCC behavior of aged materials has not been made clear by U-bend method because of γ embrittlement.

The effects of S and Mn content on the corrosion behavior of 18-8 stainless steels in the active region have been studied using mainly electrochemical means in sulfuric acid and L-ascorbic acid (C6 H8O6) solutions. The composition of sulfide inclusions (MnS) depended on the Mn/S ratio in the steels, and dissolution resistance of MnS inclusions was increased by decreases in the ratio. To the extent that MnS inclusions exist stably in the steel, they retard the cathodic reaction and the anodic dissolution reaction in the active region of the steel. When MnS inclusions were unstable and easily dissolved, however, the reactions are accelerated. Therefore, in a highly corrosive environment such as H2SO4 solution, in which the MnS inclusions are dissolved without difficulty, the corrosion resistance of the steel can be improved by decreasing the MnS content. On the other hand, in a corrosive environment such as C6H8O8 solution, in which MnS inclusions are dissolved with difficulty, corrosion resistance can be improved by decreasing the MnS contents or the Mn/S ratio.

Etude des proprietes mecaniques et de la bioabsorbabilite du poly(acide lactique) et du poly(acide glycolique). Sur la base des resultats observes, applications cliniques a la chirurgie thoracique: preparations de broches en PLA ou en composite PLA-hydroxyapatite pour la fixation de cotes fracturees; pour la reconstruction de la paroi thoracique, fabrication de reseaux mailles en PGA et PLA. Essais in vivo sur le chien

Fatigue damage accumulation induced by rotating bending (RB) and cyclic torsion (CT) is examined on a low carbon steel. The effect to the load sequence on fatigue damage accumulation was investigated microscopically as well as macroscopically. The loading type of RB-to-CT switching strengthened the fatigue life of the second stress cycle, while the fatigue damage accumulated linearly in the case of CT-to-RB loading. This trend of load sequence effect on the fatigue damage accumulation is clarified through microscopic observation of the fatigue process. The fracture mechanics-aided interpretation of the microcrack growth behavior from the slip band cracking to visual crack also supports this tendency.

The relation between the composition of MnS inclusions and crevice corrosion behavior of 18-8 stainless steel has been investigated metallographically in chloride media by an electrochemical method. It was found that in highly corrosive environments the tendency to crevice corrosion depends on the amount of MnS, while in mildly corrosive environments it depends on the amount of MnS and the Mn/S ratio. The tendency to the cessation of crevice corrosion, however, depends on the amount of MnS and the Mn/S ratio, in both environments. The morphology of corrosion near the entrance of crevices in steels in which the Mn/S ratio is large was pitting caused by preferential dissolution of the MnS inclusions. In the inner parts of the crevices, however, the matrix is dissolved preferentially independent of the Mn/S ratio. It was also determined metallographically that the corrosion potential in the inner parts of crevices is less noble than that near the entrances.

When thoracic drainage is required, the effectiveness of thoracic drainage tubes depends mainly on the intrathoracic positioning and/or patency of the tubes. The polyvinyl chloride (PVC) thoracic drainage tubes that are commonly used do not have optimum antithrombogenicity, and sometimes the tubes become ineffective because of stenosis or obstruction caused by clot formation. Silicone has excellent antithrombogenicity but insufficient strength for use as thoracic drainage tube material. Therefore, we used drainage tubes made of silicone-coated polyvinyl chloride (S-PVC) and evaluated their antithrombogenicity.The in vitro thrombus formation rate on the S-PVC surface was lower than that for PVC. Furthermore, ex vivo SEM examination revealed that the surface of S-PVC was smooth, and that hardly any platelets were adherent to it. From September, 1984, to March 1986, 15 patients underwent thoracic surgery with the use of S-PVC drainage tubes. SEM examination showed that the inner surfaces of the S-PVC drainage tubes were smooth and that platelet adhesion was minimal. On the other hand, the inner surfaces of PVC drainage tubes were coated with clots and fibrin.Accordingly, we think that S-PVC drainage tubes are very useful in cases of persistent heavy postoperative intrathoracic bleeding and/or when the period of postoperative thoracic drainage may be long.

Background: Carinal reconstruction by direct suturing is associated with a high mortality because high tension at the anastomosis can lead to tracheobronchial fistula. A new tracheal prosthesis was therefore designed for reconstruction of the tracheal bifurcation and applied for experimental carinal replacement in dogs. Methods: The main frame of the new prosthesis consists of a Y-shaped Marlex mesh tube (C.R. Bard, Inc, Billerica, Mass) reinforced with polypropylene spirals, to which collagen extracted from porcine skin is chemically conjugated to provide biocompatibility and airtightness. This conjugated collagen is composed of amorphous and sponge collagen layers. The tracheobronchial bifurcation was replaced with the prosthesis in 10 beagle dogs. Results: Eight dogs survived the postoperative period, and 2 dogs died within 4 days after the operation. Bronchoscopic examination revealed that the tracheal prosthesis was covered with smooth whitish tissue and that no stenosis or dehiscence was present in the 8 dogs even 6 months after the operation. Slight mesh exposure was recognized in 1 dog. Histologic examination revealed that approximately one half of the luminal surface was covered with ciliated columnar epithelium or nonciliated squamous epithelium. In the remaining lumen, especially in the middle portion of the prosthesis, connective tissue without epithelium was observed. Conclusions: These long-term results indicate that our bifurcated tracheal prosthesis can be used for reconstruction of the tracheobronchial bifurcation with long-term safety. (J Thorac Cardiovasc Surg 2000;119:1162-8)

A 21-year-old man with an osteosarcoma in the proximal tibia was treated by amputation, radio- and chemotherapy. Besides pulmonary metastases, intramuscular metastases repeatedly developed. Cell culture studies of pulmonary and muscular tumors showed different sensitivity patterns for cytostatic drugs; the therapy may have selected different subpopulations of the primary tumor.

We present an extremely rare case of traumatic dislocation of a sternal body segment in a child. We treated this sternal segment dislocation by means of open reduction using a newly developed pin made from poly-L-lactide containing 10 percent by weight hydroxy apatite. It is not necessary to remove this type of pin later because it is degradable and absorbed within the body within about one year after implantation. A two-year follow-up of this case revealed a good clinical result.

Publisher Summary This chapter discusses the application of immobilized enzymes for biomaterials used in surgery. The chapter investigates the replacement of various organs with this new material experimentally and clinically, including reconstruction of the trachea, chest wall, and diaphragm in the field of thoracic surgery. With the development of techniques for binding enzymes to insoluble supports, immobilized enzymes are recently utilized in various types of medical applications, especially in clinical analysis and also in therapeutic medicine. This collagen-synthetic polymer composite material is applied as a support for the immobilization of enzymes to establish its biological functions on the surface of the material, and enzymes are successfully bound to the collagen membrane layer by activation of carboxyl groups. Trypsin and urokinase are chosen with the intention of adding proteolytic (antiinflammatory) and fibrinolytic (thromboresistant) activities, respectively, to the surface properties of the composite material. Lysozyme and a peptide antibiotic, polymyxin B, are bound onto the material for the purpose of producing bacteriolytic and antibacterial biomaterials to prevent serious problems caused by bacterial infection from occurring when artificial organs and biomaterials are implanted into the body. The chapter describes the novel method of producing this enzyme-bound collagen-synthetic polymer composite material, and discusses the enzymatic characterization and several in vivo experiments made with the material carrying immobilized enzymes.

A case of localized cavitary disease in lung with multiple isolations of Mycobacterium terrae complex from the patient's sputum is presented. The patient's past history and clinical tests supported his immunologic competency. Prolonged cavitary disease with persistent positive sputum led him to submit to right lower lobe resection after 5 months of chemotherapy. Innumerable isolates of the same mycobacteria from the resected cavity with a compatible histopathologic finding supported Mycobacterium terrae complex as the definitive etiologic agent in this case.