Beware of commercial human thrombins used to stimulate cultured endothelial cells.

In the field of in vitro biocompatibility testing, the investigation of cell response at the interface with a biomaterial is of great importance; there is a need for standard conditions and thus of well-defined and reliable sources of materials for an objective evaluation of cellular function. Thrombin is often used in vitro as a stimulating agent to check the specific functions of cultured endothelial cells. In the present work, and in order to select a thrombin of commercial origin, two criteria were borne in mind: purity towards the presence of the von Willebrand factor (vWF) and effectiveness towards vWF release by human umbilical venous endothelial cells (HUVEC) that have been submitted to four human commercial thrombins. We detected the presence of vWF in some thrombin solutions that have not yet been in contact with HUVEC. The different thrombins contained vWF antigen ranging from less than 0.1 mUnit per NIH unit of thrombin (from Diagnostica Stago and Sigma Chemical Co.) to 10-20 mUnit per NIH unit of Fibrindex thrombin (from Ortho Diagnostic Systems). Thus, if vWF is present in commercial thrombins, it contributes to and overestimates the vWF appearance in the media resulting from cell stimulation. Consequently, we fixed on thrombin from Diagnostica Stago for further studies involving HUVEC on biomaterials.

[Acute positive Tdt leukemia with megakaryoblastic involvement. Apropos of an observation of an infant]. / Leucémie aiguë TdT positive avec participation mégacaryoblastique. A propos d'une observation faite chez le nourrisson.

After observation of a 10 month-old infant hospitalised for acute thrombopenia associated with signs of marked radiological hyperostosis, the initial medullograms showed a rich bone marrow free of blast cells. Subsequent complications of the thrombopenia were anemia, neutropenia and circulating blastosis. Marrow aspirations at various sites were unsuccessful. X-rays showed a worsening of the conditions and the child suffers attacks of intense pain. Ultrastructural cytochemistry and Tdt disclosed by immunofluorescence showed that the majority of blasts possessed Tdt and 2-3% were PPO positive. The presence of these 2 markers may correspond either to the presence of a promegakaryoblastic leukemia with aberrant Tdt, or to the coexistence of 2 types of blasts cells.

Endothelial cell compatibility testing of three different Pellethanes.

There is a need for viable small diameter vascular grafts, the luminal surface of which could be seeded by endothelial cells (ECs) to prevent thrombosis. In order to select candidates for EC seeding before implantation, the in vitro cytocompatibility of three different Pellethanes (polyetherurethanes) using human ECs was investigated. The methodology included two stages depending on either direct contact between cells and materials or contact between cells and material extracts, obtained under standardized conditions. By the latter method, we observed a cytotoxic effect on cell growth with 2363-55 D Pellethane extract at a 50% (v/v) concentration in the nutrient medium, likely provoked by leachables and correlated with the lowest levels of tPA, PAI1, and vWF antigens in the supernatants. By the former method, we studied EC attachment and growth. Morphology was studied by classical means and completed by scintigraphy and microautoradiography after 111Indium-labeling of the EC monolayer. Differentiation was determined by the release of vWF antigen and measurement of vWF activity (multimeric organization) after human thrombin stimulation. Despite an inhibition of proliferation for both 55 D and 75 D types (compared to the control), a functional monolayer of ECs was obtained on 75 D. Pellethane 75 D could be the best support for in vitro endothelization.