Biomedical subjects

T Fischlein

Publications and source records attributed to T Fischlein.

40 records · Page 3Linked to original sources

PubMed1987

Endothelial cell seeding of polytetrafluoroethylene vascular grafts in humans: a preliminary report.

The importance of initial human trials with autologous endothelial seeding lies not only in the implementation of a promising idea but also in the fact that canine data are only partially applicable to humans. The surface area of jugular veins in humans is much smaller than in dogs and considerably longer grafts are needed. Moreover, the reproductive capacity of adult human endothelial cells under in vivo conditions, which probably determines the success of seeding more than the seeding density, is also uncertain. Therefore the efficiency of autologous endothelial seeding in humans was investigated in 18 patients undergoing distal femoropopliteal bypass surgery. The average surface area of the jugular veins was 4.9 +/- 1.7 cm2 with an average cell yield of 32.6 +/- 18.0 x 10(4). The mean number of seeded cells per square centimeter of graft surface was 3.1 x 10(3). In a follow-up extending for 14 weeks, plasma levels of platelet factor 4 and beta-thromboglobulin as well as the platelet function in the whole blood aggregometer showed significantly better results in the seeded group. Plasma thromboxane B2, uptake and survival of indium 111-labeled platelets, and Doppler ultrasound investigations also favored the seeded group, but the results were statistically insignificant. No difference at all was found for the platelet dense granule compounds, releasable adenosine triphosphate and platelet serotonin. Thus our findings did not indicate the development of a closed endothelialized surface after 14 weeks, which is a period three times as long as the one required for confluent endothelial cell coverage in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Endothelialization of artificial surfaces: does surface tension determine in vitro growth of human saphenous vein endothelial cells?

To evaluate the possibility of providing, in vitro, an endothelial lining for artificial hearts, we cultivated adult autologous endothelial cells on two polyurethane and two silicone rubber surfaces. Over the ensuing 11-day period, we investigated the resulting cell proliferation and morphology by means of scanning electron and light microscopy. On the silicone rubber surfaces, seeding of 200,000 human saphenous vein endothelial cells per cm(2) produced an ideal cobblestone monolayer within a single day. In contrast, the polyurethane surfaces displayed an uneven, patchy distribution of endothelial cells. Scanning electron microscopy revealed microvilli and marginal overlapping in both groups. After the first day, the cell count on the polyurethane surfaces increased, whereas the count on the silicone rubber surfaces decreased. Morphologic investigations revealed that the ideally shaped cells initially on the silicone rubber had begun to overspread and subsequently to become detached, leaving denuded spheroid areas. Moreover, cultivation for 11 days on the polyurethane surfaces resulted in an unevenness of cell distribution that far exceeded the unevenness seen on the first day. Thus, despite the fact that materials with a high surface tension (such as silicone rubbers) seem to be ideal for initial cell spreading, subsequent cultivation results in cell detachment and death. On materials with a lower surface tension (such as polyurethanes), the less differentiated monolayers do at least proliferate, although their morphology remains unsatisfactory. Even if adult human endothelial cells should prove shear-stress-resistant, a minimum of 6 to 8 weeks would be required to establish autologous endothelial cell monolayers on the inner surface. Therefore, the endothelialization of artificial hearts is not possible when such hearts are used for urgent "bridging" before cardiac transplantation.

Journal Article↗

PubMed1987

PGI2 and PGE1 induce morphological alterations in human platelets similar to those of the initial phase of activation.

The effects of PGI2 and PGE1 on the ultrastructure of human platelets were studied by scanning (SEM) and transmission (TEM) electron microscopy in relation to the record of an optical aggregometer. Addition of PGI2 or PGE1 to citrated platelet-rich plasma (C-PRP) resulted in a permanent slight decrease in percent light transmission (%T) recorded by the aggregometer. SEM investigation of the platelets showed marginal pseudopods and occasional large stomata after application of prostaglandins. These alterations occurred within the initial 30 s and remained constant during the subsequent 20 min of incubation. TEM studies revealed morphological changes of alpha granules and moderately electron-dense material in the dilated profiles of the surface-connected canalicular system (SCCS). Addition of 10 microM ADP to C-PRP preincubated for 30 s with either 2 ng/ml (5 nmol/liter) PGI2 or 30 ng/ml (85 nmol/liter) PGE1 resulted in a further decrease of %T followed by a slight increase. The alterations of the aggregometer tracing were characterized in SEM by platelet shape change and the generation of primary aggregates. C-PRP samples preincubated with 3 and 9 ng/ml (8 nmol/liter and 24 nmol/liter) PGI2 or 40 and 120 ng/ml (113 nmol/liter and 338 nmol/liter) PGE1 did not produce additional changes in the aggregometer curves or in the ultrastructure of platelets in response to ADP. Our morphological study indicates that antiaggregatory prostaglandins induce an early phase of platelet activation but inhibit "shape change" and the formation of aggregates.

Adenosine Diphosphate↗

PubMedDate not supplied

Surface morphology of circulating platelets: a suggested parameter for the monitoring of endothelial seeded grafts.

For the clinical follow-up of endothelial cell seeded grafts, non-invasive but sensitive parameters are required in order to determine the extent and effectiveness of the endothelialization process. Such a very sensitive parameter was found by investigating the surface morphology of circulating platelets. This technique is based on the previous observation that characteristic alterations of platelet morphology are closely associated with the course of the aggregometer tracings. Applying these ultrastructural criteria we investigated 16 patients after distal femoro-popliteal and femoro-crural bypass surgery. Reinforced 6 mm non-seeded PTFE vascular grafts were compared with reversed autologous saphenous vein grafts. As early as 4 hours after graft implantation, a significant higher percentage of discoid platelets with marginal pseudopods--representing the earliest stage of platelet activation--as well as of spheroid "shape changed" platelets was found in patients with PTFE grafts. Moreover, perforated platelet membranes were exclusively found in the PTFE group. These findings were most distinguished 10 days postoperatively but persisted over the follow-up period of 1 year. Considering the sensitivity of the described technique it might provide a simple, reliable, and non-invasive means for the clinical assessment of successful graft endothelialization.

Blood Platelets↗