Alternative barrier technique.

This article offers an alternative barrier technique that not only places the barrier in the dental treatment room, but also places it under the direct supervision and control of the dentist. A known hepatitis B carrier was selected for immediate denture treatment to illustrate and test this proposed barrier technique.

Immediate shear stress resistance of endothelial cell monolayers seeded in vitro on fibrin glue-coated ePTFE prostheses.

The shear stress resistance of endothelial cells (EC) previously seeded onto ePTFE grafts was assessed by morphometric determination of the number of cells per cm2 of graft surface before and after exposure of 6 h of arterial blood flow interposed in the canine femoral artery. Autologous venous endothelial cells (AVEC) were harvested from the extrajugular veins of five dogs. The AVEC were cultured in vitro and seeded at a density of 150 x 10(3) cells per cm2 onto 4 mm ID ePTFE grafts precoated with fibrin glue and human fibronectin. Subsequently, the AVEC monolayers on the grafts were cultured for 8 days using a perfusion system and then implanted end-to-end in the femoral artery. All grafts remained patent (5/5). Scanning electron microscopy demonstrated complete, thrombus-free monolayers of AVEC after 6 h of arterial blood flow. The cell densities were 124 +/- 14 and 129 +/- 7 x 10(3) cells per cm2 respectively before and after implantation. It is concluded that in vitro lining of 4 mm ePTFE vascular prostheses is feasible and results in EC monolayers on the graft surface which are shear stress resistant and athrombogenic.

Improved biocompatibility of heparin surface-coated ventricular assist devices.

Heparin surface coated ventricular assist devices (VADs) and cannulas were evaluated in comparison to uncoated VADs in 10 bovine experiments (body weight 77 +/- 6 kg). All systems were primed with cristalloid solution. No systemic heparin was given. Left ventricular assist was started with a blood flow of 4.2 +/- 0.4 l/min and maintained over 6 hours. Besides hemodynamic monitoring, blood samples were taken at regular intervals for blood gas, hematological, biochemical and coagulation studies. All animals in the study group (coated) were assisted for the scheduled 6 hours without device failure. In the control group, however, total occlusion occurred in 1 VAD after 1 hour of left ventricular assist whereas the other 4 VADs remained functional throughout the protocol. Mixed venous oxygens saturation was preassist 56 +/- 12% for coated versus 63 +/- 11% for uncoated and the final value at 60 minutes after weaning was 58 +/- 16% versus 59 +/- 5% (NS). Mean hematocrit dropped from a baseline value of 33 +/- 4% for coated versus 29 +/- 8% for uncoated to 29 +/- 7% versus 30 +/- 5% (NS) after 6 hours of assist. There was no significant difference between the baseline values (5.7 +/- 3.0 mumol/l for coated versus 4.6 +/- 3.1 mumol/l for uncoated) and the 6-hour values (3.8 +/- 3.7 mumol/l versus 7.6 +/- 6.4 mumol/l) for mean plasma hemoglobine. The normalized platelet levels dropped after 10 minutes of assist to 91 +/- 21% for coated versus 94 +/- 49% for uncoated (NS) and 89 +/- 29% versus 65 +/- 44 at 6 hours (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular assist with heparin surface coated devices.

Heparin surface coated ventricular assist devices (VADs) were evaluated without systemic heparinization and compared with uncoated control VADs with systemic heparinization (bovine experiments, n = 8; bodyweight, 75 +/- 6 kg). No heparin was given in the study group, whereas heparin (300 IU/kg) was given before cannulation in the control group. Mean activated clotting time (ACT) was 127 +/- 12 sec before and 122 +/- 17 sec after 6 hours of left ventricular assist for coated (NS) versus 184 +/- 114 sec before and 650 +/- 240 sec after for uncoated (p less than 0.05) VADs. No difference was observed in platelet depletion, plasma hemoglobin, lactic dehydrogenase (LDH) production, mixed venous oxygen saturation, and VAD clot score. No VAD occlusions occurred. Ventricular assist can be achieved without systemic heparinization if VADs are improved.

[Mechanical circulatory assist using a miniaturized Archimedes screw]. / Mechanische Kreislaufunterstützung mittels miniaturisierter Archimedischer Schraube.

An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle.

Transport of tri- and dicarboxylic acids across the intestinal brush border membrane of calves.

Transport of tri- and dicarboxylic acids across the intestinal brush border membrane was investigated using citrate and fumarate as transport substrates. The experiments were performed with brush border membrane vesicles isolated from calf proximal jejunum. Citrate and fumarate uptake by the brush border membrane vesicles occurred by a common Na(+)-dependent transport mechanism that appears to be specific for tri- and dicarboxylates. The protonated forms of citrate (citrate-(1) and citrate-(2] seem to be much better transported than the trivalent form, as indicated by the strong stimulation of citrate uptake at an extravesicular pH of 5.6 compared to that at pH 7.8. Furthermore, citrate transport across the intestinal brush border membrane appears to be mediated by an electroneutral process.