The influence of 1-beta-D-arabinofuranosylcytosine on the metabolism of phosphatidylcholine in human leukemic HL 60 and Raji cells.

We report that high-dose 1-beta-D-arabinofuranosylcytosine (Ara-C) treatment leads to substantial changes of membrane lipid composition in human leukemic cell lines. HL 60 cells are at least 10- to 20-fold more sensitive to Ara-C than Raji cells. After 4 h incubation with 50 microM Ara-C, both cells show deviations in their phosphatidylcholine (PC) and triglyceride (TG) contents, starting as early as 8 h after treatment. After 24 h, the Ara-C-induced changes in lipid metabolism are accompanied by a severe loss of viability in HL 60 cells but not in Raji cells. At this time point the HL 60 cells show a 20% depletion of PC with a concomitant increase in TG of 25%, whereas in Raji cells both PC and TG are increased 20 and 22%, respectively. The addition of lysophosphatidylcholine (lysoPC) antagonizes Ara-C-induced cell death in various leukemic cell lines and primary AML blasts from patients. Since lysoPC is a direct precursor for PC and increases the PC content of the membrane, we assume that the loss of PC in the sensitive cell line HL 60 and in other cells plays a role in Ara-C-induced toxicity. Further evidence for this mechanism is presented by the observation that hexadecylphosphocholine, an inhibitor of PC synthesis shows synergistic antiproliferative effects with Ara-C. We conclude that the rapid cell lysis described during high-dose Ara-C treatment seems to be mediated by reduction of cell membrane PC content.

[Influence of the x-ray technique on evaluation of cup anteversion after total hip arthroplasty]. / Einfluss der Röntgentechnik auf die Beurteilung der Pfannenanteversion nach totaler Hüftendoprothetik.

AIM: Total hip arthroplasty (THA) is a standard procedure in orthopaedic surgery. Planar radiography of the implant is routinely performed to ensure that the operation has achieved the desired result. This study investigates the influence of varying the X-ray beam on the analysis of the radiograph. METHOD: Twenty-three patients were analysed after implantation of a total hip replacement. Besides a CT scan of the pelvis, symphysis- and hip-centred radiographs were available. The cup anteversion was calculated using two published algorithms. The CT-based data were the gold standard. RESULTS: Our study revealed a significant major error in the analysis of the symphysis-centred radiographs when compared with the hip-centered radiographs. Widmer's algorithm showed a significant superiority over Pradhan's formula. CONCLUSION: The best approximation of the anteversion angle was achieved using Widmer's technique by centering the X-ray beam onto the hip.

[Reconstruction of the tibial diaphysis with transfer of the tibial head onto the proximal fibula. Follow-up after 63 years]. / Rekonstruktion der Tibiadiaphyse mittels Tibiakopftransfer auf die proximale Fibula. Follow up nach 63 Jahren.

Osteoarthritis of the knee is often diagnosed in the orthopedic trauma practice. One major cause is axial deformity with overload. In the case presented here osteomyelitis of the tibial diaphysis developed in childhood. Surgical treatment consisted of resection of the middle tibial third and transferring the tibial head onto the proximal fibula. In this way it was possible to eradicate the osteomyelitis of the lower leg and to achieve osseous consolidation between the tibia and fibula. Despite the significant shortening of the lower limb and the varus axial deformity, the knee joint function was satisfactory in the subsequent development. After a long interval without symptoms the patient developed a medially accentuated osteoarthritis of the knee.

[Incidence of thrombophilic factor V Leiden and prothrombin G20210A mutation in Perthes disease--a pilot study]. / Häufigkeit der thrombophilen Faktor-V-Leiden- und Prothrombin-G20210A-Mutation bei Morbus Perthes--Eine Pilotstudie.

AIM: Thrombophilic mutations may play a role in the pathogenesis of the juvenile osteonecrosis of the femoral head, Perthes' disease. We investigated whether children with Perthes' disease have an increased incidence of mutations of factor V (Leiden) and prothrombin (G2O210A), which predispose to thrombosis. METHODS: For this pilot study, we analysed the data of twenty consecutive children (16 boys, 4 girls, mean age at diagnosis 6.4 years). According to Catterall's classification of severity, 2 children were in group 1, 7 in group 2, 8 in group 3, and 3 were in the most severe group 4. Mutations of factor V and prothrombin were identified in EDTA-blood by PCR amplification, digestion with restriction enzymes, and gel electrophoresis. RESULTS: Heterozygoty for the factor V mutation was detected in two children, for the prothrombin mutation in one child. Both results did not differ significantly from the incidence in Germany, which is 0.05 for factor V mutations and 0.04 for prothrombin mutations. CONCLUSIONS: For the presented group of children with Perthes' disease, we did not find an increased rate of factor V or prothrombin mutations compared to the natural incidence. In accordance to other recent studies, our results do not support a link between inherited thrombophilic mutations and Perthes' disease.

Cytidine deaminase - the methodological relevance of AraC deamination for ex vivo experiments using cultured cell lines, fresh leukemic blasts, and normal bone marrow cells.

The clinical effects of cytosine arabinoside (AraC) are highly dependent on schedule and dose. Many regimens administered to patients are derived from artificial model systems involving permanent leukemic cell lines. The differences in pharmacokinetics between the in vivo situation and such cell lines are largely neglected. However, cytidine deaminase activity in particular has a major impact on AraC pharmacokinetics by degrading AraC to its inactive metabolite AraU, and it has been shown to be of prognostic relevance in the treatment of acute myeloid leukemia. This study therefore investigated cytidine deaminase activities and AraC deamination in a variety of the most commonly used leukemic cell lines and fresh blasts and their impact on the results of an in vitro model system. It was found that cells from different cell lines (BLIN, CEM, HL60, K562, RAJI, REH, U937) vary greatly in cytidine deaminase activity (e.g., 1.89 nmol per min/mg in K562 versus 0.01 in BLIN cells) and degrade between 18.5 (BLIN) and 96.5% (REH) of AraC to AraU in the incubation medium. This degradation results in highly different AraC exposures for different cells (e.g., AUC of 960 ng per h/ml in REH versus 4048 ng per h/ml in BLIN cells) in spite of identical starting concentrations of the drug. Formation of AraCTP as the main cytotoxic metabolite of AraC is significantly influenced by the differences in cell type-dependent cytidine deaminase activity (e.g., 35.6 ng/10(7) cells in REH versus 180.2 ng/10(7) cells in BLIN cells). In contrast to permanent cell lines, fresh leukemic blasts and normal bone marrow mononuclear cells featured low AraC degradation in the model system.

Detection and determination of the major metabolites of [3H]cytosine arabinoside by high-performance liquid chromatography.

An ion-pair high-performance liquid chromatographic assay involving solid-phase scintillation detection was established for the rapid identification and determination of all major metabolites of tritium-labelled cytosine arabinoside (Ara-C) in an in vitro system. In a single run of 50 min, Ara-C, Ara-CMP, Ara-CDP-choline, Ara-CDP, Ara-U, Ara-UMP, Ara-CTP, Ara-UDP and Ara-UTP can be measured. The method is fast, sensitive, with limits of detection ranging from 40 to 200 pg (absolute), and highly reproducible.