Biomedical subjects

O E Teebken

Publications and source records attributed to O E Teebken.

23 records · Page 2Linked to original sources

PubMed1998

Thoracic computed tomography prior to redo coronary surgery.

OBJECTIVE: Median resternotomy in coronary redo surgery represents a specific risk for injury of adjacent retrosternal structures. Aiming at improved preoperative evaluation of retrosternal structures, computed tomography (CT) techniques were routinely applied in redo cases. METHODS: Of 99 patients undergoing coronary reoperations since April 93, thoracic CT scans were retrospectively analyzed for retrosternal vicinity of cardiovascular structures, condition of the ascending aorta and structural abnormalities of the sternum. RESULTS: The minimal median distance between the posterior sternum surface and the anterior aortic wall was measured at 1.9 +/- 0.9 cm, whereas the mean closest distance to the anterior right ventricular wall was 0.4 +/- 0.5 cm. In 28 cases, the distance between sternum and aorta was smaller than or equal to 1 cm. No measurable distance between the sternum and the right ventricle was noted in 41 patients. Calcification of the ascending aorta became obvious 56 times. With respect to potential injury of the ascending aorta or the right ventricle, a safe reentry by resternotomy was facilitated in all cases. However, following complete sawing, the innominate vein became injured during retrosternal dissection in two cases. Preventive femoral vessel exposure was not performed and urgent femoral cannulation (n = 1) was infrequent. CONCLUSIONS: Thoracic CT scanning prior to redo coronary surgery allows for detailed assessment of retrosternal relations and facilitates reopening of the sternum. Preventive femoral vessel exposure and lateral thoracotomies may be avoidable in many cases.

Aortography↗

PubMed1998

Tissue engineering of heart valves--human endothelial cell seeding of detergent acellularized porcine valves.

OBJECTIVE: Tissue engineering of heart valves represents a new experimental concept to improve current modes of therapy in valvular heart disease. Drawbacks of glutaraldehyde fixed tissue valves or mechanical valves include the short durability or the need for life-long anticoagulation, respectively. Both have in common the inability to grow, which makes valvular heart disease especially problematic in children. The aim of this study was to develop a new methodology for a tissue engineered heart valve combining human cells and a xenogenic acellularized matrix. METHODS: Porcine aortic valves were acellularized by deterging cell extraction using Triton without tanning. Endothelial cells were isolated in parallel from human saphenous veins and expanded in vitro. Specimens of the surface of the acellular matrix were seeded with endothelial cells. Analysis of acellularity was performed by light microscopy and scanning electron microscopy. Cell viability following seeding was assayed by fluorescence staining of viable cells. RESULTS: The acellularization procedure resulted in an almost complete removal of the original cells while the 3D matrix was loosened at interfibrillar zones. However the 3D arrangement of the matrix fibers was grossly maintained. The porcine matrix could be seeded with in vitro expanded human endothelial cells and was maintained in culture for up to 3 days to document the formation of confluent cultures. CONCLUSIONS: Porcine aortic valves can be almost completely acellularized by a non-tanning detergent extraction procedure. The xenogenic matrix was reseeded with human endothelial cells. This approach may eventually lead to the engineering of tissue heart valves repopulated with the patients own autologous cells.

Animals↗

PubMed1998

[A new concept for substitutes in vascular surgery].

In a tissue engineering approach to develop vascular grafts without disadvantages such as early thrombosis, neointimal hyperplasia, the inability to grow, aneurysm formation, as well as life-long anticoagulation, decellularized matrix tubes which were obtained by enzymatic cell extraction from a porcine aorta were seeded with human endothelial cells in vitro. This procedure led to completely biological vascular grafts with good handling qualities and sufficient burst strength, presumably suitable for implantation in the arterial circuit.

Animals↗

PubMed1997

Ischemic preconditioning prior to myocardial protection with cold blood cardioplegia in coronary surgery.

OBJECTIVE: Encouraging results on myocardial preconditioning in experimental models of infarction, stunning or prolonged ischemia raise the question whether preconditioning techniques may enhance conventional cardioplegic protection used for routine coronary surgery. METHODS: A prospective clinical trial was conducted to investigate the effect of additional ischemic normothermic preconditioning prior to cardioplegic arrest applying cold blood cardioplegia in patients scheduled for routine coronary surgery (3 vessel disease, left ventricular ejection fraction > 50%). Two cross clamp periods of 5 min with the hearts beating in sinus rhythm were applied followed by 10 min of reperfusion, each (n = 7, group I). Inducing moderate hypothermia cold blood cardioplegia was delivered antegradely. In control groups, cold intermittent blood cardioplegia (n = 7, group II) was used alone. Coronary sinus effluents were analyzed for release of creatine kinase (CK), CK-MB, lactate, and troponin T at 1, 3, 6, 9, and 12 h. In addition, postoperative catecholamine requirements were monitored. RESULTS: The procedure was tolerated well, and no perioperative myocardial infarction in any of the groups studied occurred. Concentrations of lactate tended to be higher in group I, but this difference was not significant. In addition, no significant differences for concentrations of CK, CK-MB, and troponin T were found. Following ischemic preconditioning an increased dosage of dopamine was required within the first 12 h postoperatively (group I: 2.63 +/- 1.44 microg/kg/min, group II: 0.89 +/- 1.06 microg/kg/min). CONCLUSIONS: Combining ischemic preconditioning and cardioplegic protection with cold blood cardioplegia does not appear to ameliorate myocardial protection when compared to cardioplegic protection applying cold blood cardioplegia alone. Inversely, contractile function seemed to be impaired when applying this protocol of ischemic preconditioning.

Biomarkers↗

PubMed1996

Enzymatic properties of transplanted glomerulosa cells.

There are several theories about the physiologic regeneration of adrenals and maintenance of physiologic steroid secretion after subtotal loss of adrenal cortical cells. According to the cell migration theory, adrenocytes from the zona glomerulosa migrate centripetally toward the medulla. This theory is opposed by the zonal theory according to which each zone resplenishes its cells independently. What these theories have in common is that they are based on data from the intact adrenal gland. We transplanted purified glomerulosa cells under the kidney's capsule of Lewis rats. The tissue was removed 30, 60, 90, and 150 days after transplantation to investigate the presence of two specific enzymes that are responsible for the secretion of aldosterone and corticosterone. Cytochrome p-450as is specific for glomerulosa cells producing aldosterone, and cytochrome p-45011beta is specific for fasciculata cells producing corticosterone. After sequencing the genetic code of these enzymes it became possible to demonstrate expression of the enzymes by in situ hybridization. The transplanted glomerulosa cells turned their enzymatic property to fasciculata cells expressing cytochrome p-45011beta. Our results suggest that glomerulosa cells are able to take over the physiologic function of a whole adrenal cortex in the absence of fasciculata cells, and that they are sufficient to maintain the function of the adrenal cortex.

Adrenal Medulla↗