Biomedical subjects

D Niethammer

Publications and source records attributed to D Niethammer.

347 records · Page 20Linked to original sources

PubMedDate not supplied

Quantitative assessment of mixed hematopoietic chimerism by polymerase chain reaction after allogeneic BMT.

Patients who develop mixed hematopoietic chimerism (MHC) after allogeneic bone marrow transplantation (allo-BMT) might have an increased risk of relapse or graft failure. In order to identify patients with MHC we established a quantitative polymerase chain reaction (PCR) approach to estimate the individual degree of autologous recovery and investigate the dynamics of MHC posttransplant. Therefore standardized mixed chimeric samples were generated in each individual case by mixing pretransplant recipient and donor DNA at a range of percentages. After amplification the samples were analyzed densitometrically and signal intensities were taken as the basis of individual standard curves. Subsequently posttransplant DNA samples were also analyzed, the intensity of the informative signals were compared to the standard curves and autologous recovery was expressed in percentage related to host DNA. We investigated 40 pediatric patients receiving allo-BMT by this method. 10/40 developed MHC during course of the observation period. Each patient with MHC revealed a certain dynamic. This approach might be helpful when deciding on early intervention and additional treatment to prevent graft failure or relapse.

Bone Marrow Transplantation↗

PubMedDate not supplied

Effects of cyclophosphamide and ifosfamide on neuroblastoma cells before and after activation by microsomes.

Cyclophosphamide (CP) and Ifosfamide (IF) are of great importance in the therapy of neuroblastoma (NB). They are prodrugs which have to be activated by microsomes in order to become active compounds. We established a test system which allowed the activation of CP and IF by liver microsomes in the presence of NB cells. The data from these experiments showed that neuroblastoma cells (SK-N-SH, SK-N-LO and IMR-5) were unable to activate CP and IF, but in the presence of rat liver microsomes considerable cytotoxicity was achieved, similar to those of the preactivated derivatives maphosphamide (MP) and 4-hydroxy-ifosfamide (4-OH-IF). Compared to other compounds the final metabolite acrolein contributes significantly to the cytotoxicity of CP and IF, obviously through significant lowering of the glutathione levels in the cells. The incubation system as described allows the rapid determination of the cytotoxicity of CP and IF in the simultaneous presence of microsomes. The results show great differences in the sensibility of NB cells toCP and IF.

Animals↗

PubMedDate not supplied

Positive selection of CD56+ lymphocytes by magnetic cell sorting.

A new method for the isolation of CD56+ lymphocytes from peripheral mononuclear blood cells is described. Magnetic microbeads conjugated to goat antimouse antiserum in combination with a murine monoclonal anti-CD56 antibody were coated to the CD56+ target cells. CD56+ cells were then isolated with the use of a magnetic cell sorter. The purity of the CD56+ cells was 98.4 +/- 1% (n = 12) with a recovery of the CD56+ lymphocytes of 57.2 +/- 9% (range 48-77%). The natural killer, activity of the CD56+ lymphocytes as well as the interleukin-2-induced proliferative response were not affected by the isolation procedure or the presence of the magnetic microbeads on the CD56+ cells. The described method might be a useful tool for the further characterization of CD56+ cells and their subsets and can easily be upgraded for clinical use in adoptive immunotherapy with CD56+ lymphocytes.

Adult↗

PubMedDate not supplied

Expression analysis of protein kinase C isozymes and multidrug resistance associated genes in ovarian cancer cells.

We recently demonstrated a correlation between the expression levels of the PKC eta isozyme and the MDR1 or MRP genes in blasts from AML patients, and in primary breast cancers. In order to extend these findings we analysed ovarian cancer cells from 14 ascites aspirates from 8 patients using a cDNA-PCR approach. 5 patients were examined in follow up studies. 4 out of these 5 patients received continuous chemotherapy. The relative increases in MDR1, MRP, LRP or PKC eta mRNA expression levels were monitored. In one of these patients combined significant increase in MDR1, MRP, LRP and PKC was seen. One follow up sample was obtained after chemotherapy was discontinued. In this case significant relative decreases of MDR1, LRP and PKC eta mRNA expression levels were found. Furthermore, a significant positive correlation was determined for the relative mRNA expression levels of MRP and PKC eta. These results point to a multifactorial emergence of MDR in this type of tumor with a possible involvement of the PKC eta isozyme.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

Altered expression of resistance associated genes in hepatoblastoma xenografts incorporated into mice following treatment with adriamycin or cisplatin.

To study the development of drug resistance in childhood hepatoblastoma (HB) using a model closely related to in vivo conditions, we cultivated HB xenografts from 3 patients into mice and treated these tumors with either adriamycin (ADR) or cisplatin (CIS). Determination of the relative expression levels of various resistance associated genes by a cDNA-PCR approach showed: a) Significantly enhanced MDR1 gene expression levels after treatment with ADR in each case. b) Significantly enhanced glutathione S-transferase mu (GST mu) gene expression levels after treatment with CIS in 2/3 xenografts. c) Significantly decreased levels of topoisomerase IIa (TOPO IIa) in tumors of the same two patients after treatment with either ADR or CIS. These findings give evidence that the MDR1-, GST mu- and TOPO IIa-gene products may contribute to drug resistance in HB.

ATP Binding Cassette Transporter, Subfamily B, Mem↗