Biomedical subjects
Publications and source records attributed to H H Schauwecker.
Six polyurethanes (PUs) were tested with respect to their cytocompatibility. Initial adhesion, initial spreading, and the proliferation of endothelial cells were investigated. All smooth PUs showed similar initial adhesion. Initial spreading was faster on rough PUs. Collagen coating resulted in faster initial adhesion but not better proliferation of endothelial cells.
Porous polyurethane (nonwoven) was used for the development of tracheal prosthesis, which--in a special testing design--was adapted to shape and biomechanic properties of the natural organ. This prosthesis was implanted into 19 beagle dogs using inverted, everted, and end-to-end anastomosis. Insufficiency of the anastomosis or infection was observed in the everted and end-to-end anastomosis, whereas the inverted anastomosis showed complete incorporation into surrounding tissue of the porous prosthesis but was complicated by airway obstruction due to anastomosis granuloma.
Hepatocyte cultivation in bioreactors for hybrid liver support systems is possible under two conditions: attached to a substrate like membranes or microcarriers or in suspension culture. To compare the ammonia metabolism of hepatocytes cultivated under these two conditions, cultures of primary seeded rat hepatocytes were cultivated either attached to collagen coated tissue culture plastic or as a suspension culture. During the time course of culture, the ability of hepatocytes to reduce the ammonia content of the medium decreased in both adhesion and suspension cultures, though to different extents. In suspension cultures, ammonia content was reduced from 350 microM to about 100 microM (day 4) and to about 180 microM (day 6). No significant reduction was seen on day 8 of culture. In contrast, hepatocytes attached to collagen coated dishes remained viable and functional for at least 8 days after plating, reducing ammonia content from 350 microM to 70 microM (day 4), 90 microM (day 6) and 180 microM (day 8). The period of useful metabolism of hepatocytes in bioreactors for hybrid liver support systems appears to depend on the culture conditions.
Hybrid vascular prostheses are coated with vascular endothelial cells (EC) in an attempt to reduce thrombogenicity through the metabolic activities of living cells. The present studies were planned to develop a standardized method of isolating bovine aortic EC with high yield for studies of endothelial coating of vascular prostheses. The best results were achieved using a combination of incubation with collagenase and mechanically scraping the mobilised cells from the donor vessel. Isolated adult male bovine endothelial cells were identified by the typical "cobble stone" morphology in culture and characterized by factor VIII related antigen immunofluorescence microscopy. The cells were seeded successfully on PTFE vascular prostheses.
A standardized method was developed for seeding endothelial cells (EC) in tubular vascular grafts. A rotational cell seeding device for tubular prostheses is presented and parameters influencing the kinetics of cell adhesion (rotation speed, graft diameter, cell suspension level, inoculated cell number) are reported. Seeding EC in 14 mm ID PTFE vascular grafts with rotation rate of 10 rph gave an adhesion rate of 80% in a homogeneous monolayer.
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The transfer of a free ventral and dorsal rib graft by microvascular anastomoses enables the plastic surgeon to effect bony reconstruction if the recipient site is defective. However, since this is a technically complicated procedure and associated with only partial recovery, this type of bone graft can be employed only in selected problem cases.
Polyurethane non woven membranes with microporous inner layer and macroporous outer layer where tested bacteriologically and histologically. It was proved that the macroporous layer is suitable for the ingrowth and maturing of connective tissue, while the microporous structure prevents the invasion of bacteria, nevertheless being permeable for nutrient substances. So the material could be yield favourable presupposition to achieve bioincorporation in contaminated borderlines.
Morphometric investigations on trachea kinetics in man and beagle dogs were undertaken to find out the range of motility in different moving planes. The results show a special mechanism of load distribution over the whole organ during movement. The minimal and the mean values for bending and torsion were recorded and made reproducible for to examine a trachea prosthesis in laboratory tester on its suitability for organ replacement.
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In degenerative and posttraumatic osteoarthritis of the knee joint pain is a major indication for correctional osteotomy. In additon, the degree of arthrosis, axis deviation, range of motion and derangement of ligaments must be considered. In the cases reviewed supracondylar femur osteotomy, extraligamentar and high interligamentar osteotomy of the tibial head were utilized for correction. High tibial osteotomies were performed without using stabilizing plates. Autologous as well as homologous bone implants were added as needed. From the results presented we conclude, that the different methods of correctional osteotomies are equivalent, as long as the axis deviation, which is present in most cases, is corrected into a physiological valgus position. About 3/4 of the patient operated upon were improved as far as pain, range of motion and weigthbearing are concerned. Regression of the arthrotic structural changes could be demonstrated in a few cases only.
In order to improve the accuracy of bladder and urethral pressure recording, a measurement system has been tested experimentally. It is possible to measure absolute pressure values during withdrawal of the catheter only when the system is constantly perfused. The optimum relationship between catheter diameter, perfusion rate, withdrawal rate, measurement inertia and systemic resistance has been analysed.
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Proctocolectomy with conventional ileostomy cures patients with severe ulcerative colitis but ileostomy appliances must be worn for the rest of their lives. The continent ileostomy, as devised by Kock, provides the patient with an intraabdominal ileal reservoir and a valve constructed by invaginating the efferent ileal segment into the reservoir. The patient empties his reservoir 2-3 times a day by inserting a catheter through the valve. Our experience with 14 patients is reported. The continent ileostomy was in most cases constructed as a second procedure after proctocolectomy. Minor postoperative complications, such as abscess, fistula or partial luxation of the valve were easily corrected. One patient who underwent proctocolectomy and simultaneous construction of a continent ileostomy died in acute liver failure due to a severe preexisting cirrhosis. All the other patients are continent for feces and gas and do not need external appliances. The construction of a continent ileostomy as a secondary procedure can be recommended in patients with proctocolectomy. It offers patients a life situation with differs only insignificantly from that of normal persons.
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