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Biomedical subjects

G K Uhlschmid

Publications and source records attributed to G K Uhlschmid.

31 records · Page 2Linked to original sources
PubMed1988

Endovascular stenting of veins and grafts: preliminary clinical experience.

Stenotic lesions of veins and bypass grafts are often difficult to dilate and have a high frequency of recurrence. In an effort to provide an endoluminal mechanical support, the new concept of transluminal vascular stenting was applied in four patients with stenoses of nonarterial vessels, including two with postoperative venous stenoses, one with a stenosed mesenteric artery graft anastomosis, and one with a long stenosis of the basilic vein distal to a hemodialysis shunt graft. All four were successfully treated with percutaneous transluminal angioplasty followed by endovascular stenting. All but one of the stented segments were patent, with no significant restenosis after a follow-up of 4 1/2-12 months. There have been previous reports of transluminal vascular stenting in the arterial system, and the preliminary results from this study suggest that endovascular stenting also may play an important role in the treatment of venous and graft stenoses. However, further follow-up and careful patient selection will have to be done to establish the long-term benefit of this new procedure.

Adult↗
PubMed1987

Acute and long-term effects of massive balloon dilation on the aortic wall and vasa vasorum.

To investigate the acute and long-term effects on the vasa vasorum after massive overdilation, canine aortic segments were dilated with Gruentzig balloon catheters to more than 100% over normal size. In the acute study, the significant lumen increase was the result of intimal and medial rupture with stretching and thinning of the adventitia. In these areas, the vasa vasorum were stretched and severed, causing adventitial hemorrhage. In the chronic study, areas of previous subtotal wall rupture with adventitial thinning were repaired by scar tissue. This repair included formation of a neomedia, hyperplasia of the adventitia, and proliferation of the vasa vasorum. No progression of luminal dilatation was seen. This study showed that in subtotal aortic wall rupture, even a severely damaged adventitia is capable of preserving the lumen from further dilatation and rupture until healing. Blood flow to the damaged vessel wall was reestablished by revascularization via capillary budding in the aortic wall.

Angioplasty, Balloon↗
PubMed1986

New experimental method for the repair of tracheal defects.

The use of bovine carotid artery xenografts to repair partial defects of the cervical and thoracic canine trachea as well as the covering of bronchial stumps was observed up to 32 months after surgery. Healing occurred without problems, and scanning electron microscopy revealed subsequent ciliary epithelialization of the entire graft surface (2 X 2-5 X 1.9 cm). Functionally, the grafts replaced the tracheal wall adequately. The use of resorbable suture material facilitates healing and avoids excessive formation of inflammation and granulation tissue observed with nonresorbable suture material of any kind.

Animals↗
PubMed1985

[Further developments in pancreatic islet transplantation I. Induction of selective morphological changes in the exocrine pancreas].

For pancreatic islet transplantation to become clinically applicable, chemical agents are needed which cause selective morphological alterations in the exocrine part of the organ within a few hours after application. DL-ethionine (Aet), cerulein (Cd), seleno-DL-methionine (SeMet) and seleno-DL-ethionine (SeAet) were given to rats during various time periods. At 4 h after i.p. injection, 40 mg/kg SeMet caused the greatest selective morphological alterations in the exocrine pancreas. Acinar structure disappeared, the exocrine cells were abnormal and their nuclei had various dimensions and forms. There were, however, no alterations in the islet cells. At this time, neither Aet, Cd, nor SeAet produced similar changes. SeMet was the most toxic substance and was taken up in the shortest time and in the greatest amount. This selective destructive SeMet effect allows better isolation of the islets from exocrine tissue thereby increasing islet yield and decreasing transplantation volume. Better islet purification may prevent an early rejection.

Animals↗
PubMed1985

Intravenous spiral support for the prevention of outflow-tract stenosis in av-shunts for hemodialysis?

Intraluminal spiral support of bovine heterografts (Solcograft-P) offers promising mechanical characteristics for av-shunts. Using a tunneling technique the spiral prevents twisting and kinking during subcutaneous placement and allows prolonged and vigorous post-puncture compression for hemostasis without compromising shunt flow. Canine experiments (femoro-femoral loop) suggest that additional insertion of the spiral into the efferent vein for some centimeters can prevent or delay the development of outflow-tract stenosis, the main cause of late shunt failure (0% (0/5) vs. 75% (3/4) significant stenosis; total patency rate 90% (9/10); follow-up 3 months). Preliminary clinical results with brachio-cephalic/basilic av-shunts in the forearm (loop) support our experimental investigations. In all eight patients the shunt is functioning perfectly without reinterventions being necessary (mean follow-up 8.8 months, totally 55 dialysis months). In five patients the shunt was used early for hemodialysis (days 1-10 post operation). Angiographically, stenoses developed in the outflow-tract in five of six shunts, but only one stenosis was observed in the spiral-supported venous segment where it usually occurs. In some cases shunt function was preserved by collaterals from the nonstenotic spiral-supported venous segment despite occlusion of the main efferent vein. Thus, it appears that a spiral placed into the graft and efferent vein is suitable to prolong the functional life of av-shunts.

Adult↗
PubMedDate not supplied

New versatile, elastomeric, degradable polymeric materials for medicine.

The present investigation was focused on the cell compatibility of recently developed biodegradable polyesterurethane-foam (DegraPol-foam) to chondrocytes and osteoblasts. Both chondrocytes and osteoblasts, isolated from adult male rats, exhibited relatively high cell adhesion on DegraPol-foam. Scanning electron microscopy (SEM) showed that cells grew on the surface and into the open cell pores of the foam. Morphologically, cells found on the surface of the foam exhibited a flat cell appearance and built a confluent cell multilayer. In contrast, inside the foams cell showed rounded morphology building cell aggregates and cell islets. In addition, chondrocytes and osteoblasts proliferated on the DegraPol-foam and preserved their phenotype for up to 2 weeks. During degradation of these polymers, small crystalline particles of short-chain poly[(R)-3-hydroxybutyric acid] (Mn approximately 2300) (PHB-P) and lysine methyl ester are released. Therefore, lysine methyl ester and PHB-P, as possible degradation products of the polymer, are investigated here for their effects on macrophages and osteoblasts. Results obtained in the present study clearly indicate that macrophages and, to a lesser degree, osteoblasts have the ability to take up (phagocytose) PHB-P. At low concentrations, particles of PHB failed to induce cytotoxic effects or to activate macrophages. Osteoblasts showed only limited PHB-P phagocytosis and no signs of any cellular damage. At high concentrations of PHB-P, the cell viability of macrophages and to a lesser extent of osteoblasts was affected.

Animals↗