A new type of matrix vesicles is found in fetal bovine tracheal cartilage.

Using 4-month-old fetal bovine tissue, the properties of the tibia epiphyseal cartilage matrix vesicles, a type of endochondral ossification tissue, were compared with those from tracheal cartilage. The matrix vesicle fractions, obtained by collagenase digestion and differential centrifugation, were subjected to sucrose-density-gradient centrifugation. Alkaline phosphatase activity, protease activity, and lacatate dehydrogenase activity were assayed for the marker enzyme of the matrix vesicles. Matrix vesicles containing alkaline phosphatase, metalloprotease, and lacatate dehydrogenase were found in the tibia epiphyseal cartilage at a density of 1.11 g/ml. In surprising contrast, we also found matrix vesicle-like vesicles with a high density of 1.24 g/ml in the tracheal cartilage. These also contained alkaline phosphatase and lactate dehydrogenase, but not metalloprotease. The electrophoretic profiles of the lactate dehydrogenase isoenzymes from the matrix vesicle and matrix vesicle-like vesicles were identical with those of chondrocyte cytosolic lactate dehydrogenase. Aldolase, aspartate: 2-oxoglutarate aminotransferase, alanine: 2-oxoglutarate aminotransferase, glucose-6-phosphatase, glutamate dehydrogenase, catalase, and cytosolic enzymes except for lactate dehydrogenase were not detected in these vesicles. These results suggest the presence of a mechanism for specific uptake of cytosolic lactate dehydrogenase in both vesicles. In this study, a new type of matrix vesicles without protease was found in the tracheal cartilage, a kind of permanent cartilage, but not in the tibia epiphyseal cartilage, which is replaced by bone tissue.

A transient increase in endogeneous erythropoietin levels after paediatric liver transplantation.

We investigated whether liver transplantation affects endogeneous erythropoietin (EPO) synthesis. Serum EPO levels were measured before transplantation and during the peri-transplant period in ten consecutive paediatric patients who had received a liver allograft without recombinant EPO therapy. All patients were anaemic on post-operative day 1 (POD 1); however, the haemoglobin levels of three patients gradually increased and required phlebotomy on POD 5-9. The serum levels of EPO in all patients were within the normal range before surgery, but six of the ten patients had a transient increased level of EPO at 1248 h after transplantation. A transient increase of endogeneous EPO following paediatric liver transplantation may be associated with extramedullary erythropoiesis in human liver grafts.