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Purpose: The reactivity of subendothelium generated by endothelial cells attained from the umbilical cord of a newborn girl from a patient with type I von Willebrand's disease was evaluated., Material and Methods: Platelet adhesiveness was assessed by means of "ex vivo" blood perfusion systems (shearing coefficients from 300 to 1,300 s-1), on umbilical artery subendothelium and over the extracellular matrix (ECM) generated by cultured endothelial cells attained from the umbilical cord of a newborn baby from a type I von Willebrand mother., Results: By means of an ELISA technique, a significant reduction of both the vWF secreted into the culture (p < 0.05) and of that associated with ECM (p < 0.05) was noticed. The two subendothelial surfaces examined supported a lesser extent of platelet adhesion than the control surfaces from healthy individuals in the perfusion tests at 1,300 s-1 (p < 0.05). The experimental results did not agree with the lack of clinical manifestations and laboratory abnormalities in the propositus at age 3., Conclusions: These findings suggest that the endothelial cells cultured from the tissues of a newborn baby from a type I von Willebrand woman expressed less vWF, at the same time confirming the importance of vWF bound to connective tissue in sustaining platelet adhesion. The data attained here illustrate the complex model of inheritance of moderate von Willebrand's disease, along with the technical limitations of cell culture studies. Such observations must be borne in mind whenever any experimental approach is performed with material attained from ill-differentiated tissues such as the umbilical cord vein.

Cultured endothelial cells are currently used as a model for the study of the interaction of platelets with the vascular wall under flow conditions. Little is known about the influence of cell-culture conditions on the preservation of the original characteristics of primary tissues. In our study, the reactivity of platelets towards extracellular matrices produced by endothelial cells from different passage numbers was morphometrically evaluated. The presence and distribution of the extracellular von Willebrand factor was analyzed by immunofluorescent techniques. Morphology of endothelial cells in culture varied dramatically along the culture and polymorphism increased clearly at fourth or fifth passages. Extracellular matrix thrombogenicity decreased significantly from the fifth passage number. Simultaneously, von Willebrand factor distribution in ECM changed its typical pattern. Our results confirm that the extracellular matrix produced by human umbilical vein derived-endothelial cells constitutes a good model for the study of platelet adhesion onto vascular subendothelium. The limited viability of ECs and the variation in the thrombogenic properties of ECM formed after multiple passages must be taken into account when these cells or their products are used in experimental research.

Free erythrocyte protoporphirin (FEP), along with diverse haematologic and iron metabolism data, were determined in 60 carriers of the thalassaemic trait (29 beta and 31 delta beta). FEP rates were significantly higher in thalassaemia carriers (39.04 +/- 14.12 micrograms/dl) than in a control group (24.95 +/- 4.70 micrograms/dl) (p less than 0.05). No correlation between FEP and any other iron metabolism parameter, or the severity of anaemia, was found. No FEP differences appeared between the beta (41.06 +/- 16.5 micrograms/dl) and delta beta (37.1 +/- 11.06 micrograms/dl) traits, so, although FEP rates are increased in thalassaemia carriers, they are useless in differentiating between the commonest thalassaemic forms in our country.

Red-cell deformability was assessed with the Hanss' haemorheometer in 63 carriers of the thalassaemic trait (20 beta and 43 delta beta). Impaired deformability (rigidity index 10.5 +/- 1.4) was present in 80% of the carriers of both beta- and delta beta-traits, as compared with a control group (rigidity index 8.7 +/- 0.6). No correlation was found between such indices and several parameters capable of influencing upon red-cell deformability, namely, MCV, MCH, RDW and MDA. The possibility of any impairment of lipid compounds in red cell membrane is suggested as a cause of decreased deformability in thalassaemia carriers.