Search PubMed⌕ Search

Biomedical subjects

M Grimm

Publications and source records attributed to M Grimm.

At least 145 records · Page 8Linked to original sources
PubMed1992

Improved biocompatibility of bioprosthetic heart valves by L-glutamic acid treatment.

Treatment of glutaraldehyde-fixed pericardium with L-glutamic acid and storage in bacteriostatic preservatives (paraben) stably antagonizes free, reactive aldehyde groups within the fixed bioprosthetic heart valve tissue. In 63-day subcutaneous implants in rats, the calcification rate of this treatment (13.3 +/- 2 mg calcium/g wt tissue) was markedly reduced as compared to conventionally treated tissue (169 +/- 24 mg/g; p less than 0.05). To test the influence of tissue-released toxic aldehydes on spontaneous endothelial cell ingrowth in vivo, vascular grafts (8-cm long, 6-mm diameter) from fixed pericardium treated with L-glutamic acid were interposed into the carotid arteries in ten sheep. They were compared to grafts from conventionally treated pericardium implanted at the contralateral side. Following 3 months of implantation, planimetry revealed 49% +/- 20% of the surface of conventionally preserved pericardium to be covered with red thrombus, but only 12% +/- 5% in L-glutamic acid treated pericardium (p less than 0.05). The ultrastructural findings of a closed endothelial cell layer on the graft surface reveals the new technique to be a promising approach towards increased biocompatibility of aldehyde-fixed bioprosthetic heart valves.

Animals↗
PubMed1992

Endothelial cell lining of bioprosthetic heart valve material.

In this in vitro study, the growth properties of cultured endothelial cells on conventionally treated pericardial valve material were measured. These data were compared to endothelial cell proliferation on an alternatively treated valve material. This alternative preservation procedure was developed in order to bind free, residual glutaraldehyde in the valve tissue by reaction with L-glutamic acid. In order to optimize endothelial cell attachment and proliferation, fibronectin and fibrillar collagen type I were tested as surface precoating substances. Cell viability of the seeded cells was evaluated by means of proliferation kinetics, antithrombotic activity, and morphological appearance. Endothelial cell death occurred within the first 2 days after seeding on conventionally treated valve tissue, independent of the type of precoating. On alternatively treated tissue, regular endothelial cell proliferation was observed. Precoating with fibrillar collagen markedly increased endothelial cell attachment and proliferation as compared to fibronectin. Maintenance of antithrombotic activity of the seeded cells was proven by regular release of prostacyclin.

Animals↗
PubMed1992

One and one-half year experience with unilateral and bilateral lung transplantation.

Lung transplantation has now become an established form of treatment for end-stage pulmonary parenchymal and vascular diseases. Despite its wide acceptance, technical aspects are still in discussion. We report on the initiation of our own lung transplant program and the technical changes we have performed during our first 1 1/2-year experience. During that period of time, we have performed 26 lung transplantations (16 single lung [SLTX] and 10 bilateral lung transplantations [BLTX]). Three-month survival for the whole group was 74% (69% for the SLTX group and 77% for the BLTX group). No instance of bronchial dehiscence was observed; however, there were eight cases of bronchial stenosis: six were managed by silicone stent insertion, one by bronchoplastic correction, and one by retransplantation. Changes in the technique of the bronchial anastomosis together with the addition of prednisone to the immediate postoperative immunosuppressive regime resulted in almost complete avoidance of these problems.

Adult↗
PubMed1992

Endothelial cell lining of bioprosthetic heart valve materials.

To investigate the conditions for endothelial cell lining of glutaraldehyde-treated bioprosthetic heart valves, we examined in vitro the growth properties of endothelial cells on clinically used pericardial valve material and on glutaraldehyde-fixed pericardium treated with L-glutamic acid. To improve endothelial cell attachment to the valvular surface, we precoated both materials either with fibronectin or with fibrillar collagen (95% type I, 5% type III). Toxicity of glutaraldehyde, released from clinically used valve material, caused endothelial cell death, independent of the type of precoating. Treatment of the valve material with L-glutamic acid resulted in regular endothelial cell proliferation. We found that collagenous precoating, compared with fibronectin precoating, markedly enhanced endothelial cell proliferation and attachment (p less than 0.05). Maintenance of antithrombogenic potency of the seeded cells on L-glutamic acid-treated valve material was proved by regular release of prostacyclin. We conclude that bioprosthetic heart valve materials can be lined with endothelial cells if toxic glutaraldehyde released from the bioprostheses is eliminated.

Animals↗
PubMed1992

Implantation of in vitro endothelialized polytetrafluoroethylene grafts in human beings. A preliminary report.

To assess the impact of in vitro endothelialization on prosthetic graft patency, we performed femorotibial reconstruction in four patients. Polytetrafluoroethylene grafts (6 mm), lined with cultivated autologous endothelial cells, harvested from the veins of the forearm, were used. Autologous endothelial cells were harvested enzymatically and characterized by morphology and factor VII staining. After a cultivation period of 17 to 23 days, the cell count increased from 27 +/- 3 x 10(4) endothelial cells to 5.4 +/- 1.1 x 10(6). Endothelial cell seeding on polytetrafluoroethylene prostheses was then performed. To improve endothelial cell attachment to the graft surface, polytetrafluoroethylene grafts (60 to 70 cm; 6 mm diameter) were precoated with fibrin glue containing fibrin and fibronectin and the fibrinolysis inhibitor aprotinin. Seeding density of 49 +/- 10 x 10(3) endothelial cells per square centimeter yielded a preconfluent monolayer immediately after seeding, as demonstrated by scanning electron microscopy. A second cultivation period of 6 days, after seeding and before implantation, was necessary for establishment of a confluent monolayer and to allow for maturation of the endothelial cell cytoskeleton as well as production and excretion of extracellular matrix. Grafts endothelialized in vitro were implanted in four patients requiring femorotibial reconstruction. Scintigraphic studies with indium 111-labeled platelets demonstrated little or no platelet deposition, indicating persistent endothelialization. All grafts remained patent at 3 months after implantation.

Aged↗
PubMed1992

Prospective clinical study with in vitro endothelial cell lining of expanded polytetrafluoroethylene grafts in crural repeat reconstruction.

A nonrandomized prospective clinical study was undertaken to evaluate the technique and efficacy of in vitro endothelial cell lining of synthetic grafts. Twenty-six patients (10 men and 16 women with a mean age of 68.4 years; range, 49 to 80 years) with end stage chronic peripheral vascular disease requiring reoperation were entered into the study. In 13 patients venous endothelial cells were harvested 4 to 7 weeks before operation, grown to confluency in culture flasks, and seeded onto the inner surface of expanded polytetrafluoroethylene grafts. Thirteen patients received untreated expanded polytetrafluoroethylene grafts and served as a control. A scoring system with use of intraarterial angiography was used to assess disease severity. No statistically significant differences in angiographic score were seen between the two groups, indicating comparable severity of disease. Early secondary graft patency (0 to 30 days) was 92% for the in vitro endothelial cell lining group and 53% for control patients. The amputation rate after 18 months for the in vitro endothelial cell lining group was 15%, with a 31% rate in the control group. The functional performance of the in vitro endothelial cell lining bypasses was superior to that of untreated bypass grafts during the observed follow-up period. These early results suggest that in vitro endothelial cell lining is a method that can reduce the early occlusion rate now seen after repeat reconstruction of crural vessels.

Aged↗
PubMed1992

Improved endothelialization of postfixation treated biological vascular grafts.

Preliminary in vitro and in vivo studies have shown that endothelialization is improved by a detoxifying postfixation treatment of glutaraldehyde (GA) fixed bovine pericardial patches and grafts. To test whether this is also true for GA tanned human vein (HUV) grafts, patches of commercially available HUV grafts (MHUV), postfixation treated HUV grafts (PTHUV) and GA fixed HUV granfts (GAHUV) were endothelialized in vitro. Eight pairs of MHUV and PTHUV grafts were implanted as femoropopliteal grafts in eight sheep. Endothelial cell adherence was significantly better on PTHUV (11910 +/- 4413 cells/cm2) than on MHUV (6545 +/- 2835 cells/mm2; p = 0.0007) and on GAHUV (3563 +/- 1638; p = 0.0001) one day after cell seeding. After eight days of culture significantly more cells spread on PTHUV material than on MHUV (p = 0.0002), but none of the cultures on GAHUV remained viable. Four PTHUV grafts occluded in the femoropopliteal position, mostly because of kinking, so that only in four pairs of grafts could the thrombus-free surface be compared by planimetry. Again PTHUV material was covered more by endothelial cells than was MHUV material. On PTHUV endothelial cells spread directly on the graft material while on MHUV these cells spread on a layer of fibrin and macrophages. Postfixation treatment of GA-fixed biological graft material by amino-acid solutions improves the biocompatibility of the material and enhances in vitro as well as spontaneous in vivo endothelialization.

Animals↗
PubMed1992

New aspects of the degeneration of bioprosthetic heart valves after long-term implantation.

Bioprosthetic heart valves removed 76 to 150 months after implantation were morphologically investigated to correlate structural alterations with clinical failure modes. Traditional morphologic methods of evaluating valvular heterografts, such as microradiography and electron microscopy, were complemented by undecalcified ground sections, a new technique for analyzing the distribution of mineral deposits. Apart from well-investigated mechanisms that accelerate tissue degeneration, our observations point to additional facts: (1) phagocytosis of collagen fibrils and elastic material by macrophages and foreign body giant cells in areas near tears and perforations and (2) initial calcification indicated by delicate crystals in the intercellular space arranged in close relation to the periodicity of the cross-striation pattern of collagen fibrils. The present report not only calls attention to degenerative changes that are enhanced by mechanical stress but also underlines phagocytosis as an important mechanism in the destruction of bioprosthetic heart valves.

Bioprosthesis↗
PubMed1992

Glutaraldehyde affects biocompatibility of bioprosthetic heart valves.

A marked release of glutaraldehyde from commercially available pericardial bioprosthetic heart valve (BHV) material in washing solutions was found by high performance liquid chromatography (up to 1.8 ppm of glutaraldehyde per gram of dry tissue). In vitro endothelial cell proliferation rate was impaired dose-dependently in the presence of increasing glutaraldehyde concentrations of the cultivation medium (r = 0.9; p less than 0.05). Cultivation of endothelial cells was impossible on the surface of commercially available BHV material, but successful and uninhibited when toxic glutaraldehyde ligands of the BHV material were antagonized by treatment with L-glutamic acid.

Animals↗
PubMed1991

Improved spontaneous endothelialization by postfixation treatment of bovine pericardium.

The longstanding release of locally cytotoxic glutaraldehyde concentrations from fixed biological materials is one reason for the lack of spontaneous endothelialization in vivo and in vitro of biological grafts (and valves). Preliminary studies have shown that bovine pericardium postfixation-treated with aminoacids may be endothelialized in vitro. To test whether such treatment improves spontaneous endothelialization in vivo 8 cm long segments grafts (6 mm I.D.) were interposed into the carotid arteries of 10 sheep. Ten grafts were sewn from postfixation treated pericardium (PTP), 4 from standard glutaraldehyde fixed pericardium (GAP) and 6 polytetrafluoroethylane (PTFE) grafts were implanted to study the degree of spontaneous endothelialization. In two pregnant animals, all grafts occluded (2 PTP, 1 GAP, 1 PTFE). In the remaining animals 1 additional PTFE graft occluded and 2 PTFE and 1 GA grafts showed significant thrombotic obstruction. The patent grafts were harvested at 3 months and the surface covered with red thrombus was determined by planimetry. PTP grafts had significantly less (12.2% +/- 15%) thrombotic appositions than glutaraldehyde treated grafts (49% +/- 20%; P = 0.01) and PTFE grafts (40.5% +/- 13%; P = 0.01). In the central areas of the PTP grafts, endothelial cells spread directly on the collagenous matrix and produced a basal lamina. In GAP, endothelial cells spread on amorphous material or macrophages and in PTFE grafts, only a neointima composed of myofibroblasts was endothelialized. Neutralization of glutaraldehyde concentrations by postfixation with aminoacids improves spontaneous endothelialization in vivo in biological materials.

Animals↗
PubMed1991

Biocompatibility of aldehyde-fixed bovine pericardium. An in vitro and in vivo approach toward improvement of bioprosthetic heart valves.

Aldehyde-induced side effects limit the clinical usefulness of bioprosthetic heart valves. Treatment of aldehyde-fixed pericardium with L-glutamic acid at pH 3.5 and storage in a nontoxic, bacteriostatic solution resulted in a lower degree of calcification in 63-day subcutaneous implants in rats (13.3 +/- 2 mg calcium per gram dry weight of tissue), as compared with commercially available tissue (169 +/- 24 mg/gm, p less than 0.05). Endothelial cells died within 1 day after seeding on the commercial tissue; however, considerable endothelial cell proliferation was measured, even 14 days after seeding on L-glutamic acid-treated pericardium. Improved biocompatibility of this alternative treatment may be due to stable chemical binding of free, reactive aldehyde groups.

Animals↗
PubMed1991

[Uni- and bilateral lung transplantation: surgical results and experiences of the 1st year. Vienna Lung Transplant Group].

Transplantation of the lung has gained increasing importance during the last years and is now an established therapy for end stage lung disease. After a 3 years period of preparation the first single lung transplantation (SLTX) was performed at the Second Surgical Department of the University of Vienna in November 1989, followed by the first double lung transplantation (DLTX) in April 1990. Until the end of 1990 11 patients underwent SLTX and 6 DLTX. 7 of the 11 SLTX patients and 4 of the 6 DLTX patients are at present alive with significantly improved lung function and therefore markedly improved quality of life.

Adult↗
PubMed1991

[Uni- and bilateral lung transplantation: functional results. Vienna Lung Transplant Group].

At the end of December 1990 11 patients had survived lung transplantation at the 2nd Department of Surgery, University of Vienna. In these patients 7 single lung (SLTX) and four bilateral lung transplantations (DLTX) were performed. The indication for operation in 6 cases was emphysema, in 2 cases mucoviscidosis, in 2 cases pulmonary fibrosis, and in 1 case secondary pulmonary hypertension, following operation of a ductus Botalli. By means of fitness tests, blood-gas analysis, pulmonary function tests and ventilation respectively perfusion scan a marked improvement of the clinical status of the patients following lung transplantation could be shown.

Adult↗
PubMed1991

Growth properties of cultured human endothelial cells on differently coated artificial heart materials.

The cultivation of autologous endothelial cells on the blood surface of artificial hearts might prevent their detrimental thromboembolic complications. To investigate the growth characteristics of endothelial cells on theoretically suitable biomaterials, we compared three polyurethanes (Pellethane, Biomer, Enka) and three silicone rubbers (Elastosil, 3145 RTV, Medical Adhesive). All synthetic surfaces were precoated with an extracellular matrix (group 1), fibronectin (group 2), or a glutaraldehyde-preserved cellular matrix (group 3). After the seeding of 2.5 x 10(4)/cm2 human endothelial cells into the various surfaces, primary adherence, growth kinetics, and maintenance of monolayer integrity were studied for 13 days. On the three polyurethanes all precoating procedures resulted in endothelial cell proliferation and the formation of persistent monolayers. In contrast, on silicone rubbers a persistent coverage with a confluent endothelium could be achieved only on the glutaraldehyde-preserved cellular matrix. When endothelial cell growth was quantitatively assessed on all precoating substrates, the glutaraldehyde-preserved cellular matrix proved to be far superior on each of the synthetics (p less than 0.001). These results demonstrate the theoretical feasibility of endothelialization of artificial hearts in vitro. Provided such an endothelium can withstand the mechanical forces within an artificial heart, in vitro endothelialization might contribute to a regained attractiveness of the elective long-term implantation of artificial hearts.

Biocompatible Materials↗
PubMed1990

[Glutaraldehyde residues in heart valve prostheses].

Bioprosthetic heart valves prepared from glutaraldehyde-pretreated bovine pericardium are used to replace diseased human cardiac valves. Mineralisation in the course of time and toxic effects are possibly caused by glutaraldehyde residues. Different washing methods carried out before transplantation are compared with regard to the different ability of glutaraldehyde extraction.

Animals↗
PubMed1990

[Experimental studies of extracellular matrix constituents for coating artificial prostheses before endothelialization].

Endothelialization seems to be a possibility to reduce thrombogenicity of artificial vascular prostheses. We have been occupied to find an ideal coating for the cells. Substances of extracellular matrix (ECM) were used: human fibronectin (HFN), laminin, collagen type I + III + IV. We have compared the influence of these materials with regard to adherence, sheer stress resistance and growth of cultivated human vena saphena endothelial cells (SEC). There was not any statistically significant difference according to cell proliferation. During a cultivation period of 7 days SEC increased by population doubling number 5 corresponding to a population doubling time of 76 hours. PTFE prostheses were coated with the materials, seeded with SEC and exposed to sheer stress in a physiological perfusion unit. Adherent SEC were counted after 24 hours of perfusion. Counts were correlated to the number of seeded cells. After perfusion only 23 +/- 4%, resp. 25 +/- 6% of cells were counted on collagen I + IV + HFN and on collagen I + IV + laminin. We found better results on collagen I + III and on collagen I + III + HFN; there were adherent 55 +/- 5%, resp. 53 +/- 7% after perfusion. These results document that there is no difference for SEC cultivation on different native components of basal membrane, under sheer stress conditions there seems to be differences in cell adherence.

Blood Vessel Prosthesis↗
PubMed1990

Diagnosis of perioperative myocardial infarction by considering relationship of postoperative electrocardiogram changes and enzyme increases after coronary bypass operation.

We report the results of enzyme determinations in sera from 88 patients, 65 of whom showed inconspicuous reconvalescence, 14 who had myocardial infarction within 24 h (MI 1) after bypass surgery, and nine with myocardial infarction between 24 and 48 h postoperatively (MI 2). We wanted to determine whether the consequent measurement of activities of total creatine kinase (CK), CK isoenzyme MB (CK-MB), lactate dehydrogenase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase, conducted as a part of routine laboratory diagnostics, provided meaningful information for diagnosing infarcts besides that obtained from the electrocardiogram. The postoperative mean values of the enzyme activities in blood were significantly different among the three groups; however, only a combined evaluation of CK and CK-MB by means of a discriminant analysis allowed the prediction of MI (sensitivity: MI 1 = 98.5%, MI 2 = 95.4%; specificity: MI 1 = 71.4%, MI 2 = 81.8%). CK greater than 600 U/L or CK-MB greater than 45 U/L supports the diagnosis of acute MI.

Adult↗