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Biomedical subjects

E J Muller

Publications and source records attributed to E J Muller.

15 recordsLinked to original sources
PubMed2000

Cyclopentenyl cytosine inhibits cytidine triphosphate synthetase in paediatric acute non-lymphocytic leukaemia: a promising target for chemotherapy.

Cytidine triphosphate (CTP) synthetase is a key enzyme in the anabolic pathways of cytosine and uracil ribonucleotide metabolism. The enzyme catalyses the conversion of uridine triphosphate (UTP) into CTP, and has a high activity in various malignancies, which has led to the development of inhibitors of CTP synthetase for therapeutic purposes. We studied both CTP synthetase activity and ribonucleotide concentrations in leukaemic cells of 12 children suffering from acute non-lymphocytic leukaemia (ANLL), and performed incubation experiments with cyclopentenyl cytosine (CPEC), a nucleoside analogue that is capable of inhibiting CTP synthetase. The CTP synthetase activity in ANLL cells (5.1+/-2.3 nmol CTP/mg/h) was significantly higher compared with granulocytes of healthy controls (0.6+/-0.4 nmol CTP/mg/h, P=0.0002), but was not different from the CTP synthetase activity in non-malignant CD34+ bone marrow cells (5. 6+/-2.4 nmol CTP/mg/h). Major shifts were observed in the various ribonucleotide concentrations in ANLL cells compared with granulocytes: the absolute amount of ribonucleotides was increased with a substantial rise of the CTP (2.4 versus 0.4 pmol/microg protein, P=0.0007) and UTP (8.7 versus 1.6 pmol/microg protein, P=0. 0007) concentrations in ANLL cells compared with granulocytes. Treatment of ANLL cells in vitro with CPEC induced a major depletion (77% with 2.5 microM of CPEC) in the concentration of CTP, whilst the concentrations of the other ribonucleotides remained unchanged. Therefore, the high activity of CTP synthetase in acute non-lymphocytic leukaemic cells can be inhibited by CPEC, which provides a key to a new approach for the treatment of ANLL.

Adolescent↗
PubMed1999

HGF/SF and its receptor c-MET play a minor role in the dissemination of human B-lymphoma cells in SCID mice.

The MET protooncogene, c-MET, encodes a cell surface tyrosine kinase receptor. The ligand for c-MET is hepatocyte growth factor (HGF), also known as scatter factor (SF), which is known to affect proliferation and motility of primarily epithelial cells. Recently, HGF/SF was also shown to affect haemopoiesis. Studies with epithelial and transfected NIH3T3 cells indicated that the HGF/SF-c-MET interaction promotes invasion in vitro and in vivo. We previously demonstrated that HGF/SF induces adhesion of c-MET-positive B-lymphoma cells to extracellular matrix molecules, and promoted migration and invasion in in vitro assays. Here, the effect of HGF/SF on tumorigenicity of c-MET-positive and c-MET-negative human B-lymphoma cell lines was studied in C.B-17 scid/scid (severe combined immune deficient) mice. Intravenously (i.v.) injected c-MET-positive (BJAB) as well as c-MET-negative (Daudi and Ramos cells) B-lymphoma cells formed tumours in SCID mice. The B-lymphoma cells invaded different organs, such as liver, kidney, lymph nodes, lung, gonads and the central nervous system. We assessed the effect of human HGF/SF on the dissemination of the B-lymphoma cells and found that administration of 5 microg HGF/SF to mice, injected (i.v.) with c-MET-positive lymphoma cells, significantly (P = 0.018) increased the number of metastases in lung, liver and lymph nodes. In addition, HGF/SF did not significantly influence dissemination of c-MET-negative lymphoma cells (P = 0.350 with Daudi cells and P= 0.353 with Ramos cells). Thus the effect of administration of HGF/SF on invasion of lymphoma cells is not an indirect one, e.g. via an effect on endothelial cells. Finally, we investigated the effect of HGF/SF on dissemination of c-MET-transduced Ramos cells. In response to HGF/SF, c-MET-transduced Ramos cells showed an increased migration through Matrigel in Boyden chambers compared to wild-type and control-transduced Ramos cells. The dissemination pattern of c-MET-transduced cells did not differ from control cells in in vivo experiments using SCID mice. Also no effect of HGF/SF administration could be documented, in contrast to the in vitro experiments. From our experiments can be concluded that the HGF/SF-c-MET interaction only plays a minor role in the dissemination of human B-lymphoma cells.

3T3 Cells↗
PubMed1999

Cytidine triphosphate synthase activity and mRNA expression in normal human blood cells.

Cytidine triphosphate (CTP) synthase is one of the key enzymes in pyrimidine nucleotide anabolic pathways. The activity of this enzyme is elevated in various malignancies including acute lymphocytic leukemia (ALL). In this study we investigated the activity of CTP synthase in various human blood cells isolated from healthy volunteers by density centrifugation and elutriation centrifugation. We also investigated the mRNA expression of CTP synthase in lymphocytes and monocytes. The highest activity of CTP synthase was found in thrombocytes (6.48 nmol CTP x mg(-1) x h(-1)), followed by that of monocytes (2.23), lymphocytes (1.69), granulocytes (0.52) and erythrocytes (0.42). The activity of CTP synthase in whole blood samples was at an intermediate level (1.27). The mRNA expression of CTP synthase in monocytes was comparable to that observed in lymphocytes.

Blood Platelets↗
PubMed1998

Hepatocyte growth factor/scatter factor (HGF/SF) is produced by human bone marrow stromal cells and promotes proliferation, adhesion and survival of human hematopoietic progenitor cells (CD34+).

The fate of hematopoietic progenitor cells (HPCs) in the bone marrow (BM) microenvironment is determined by two different interactions: 1) they adhere (via integrins) to both extracellular matrix molecules and BM stromal cells; and 2) stromal cells produce cytokines that influence their survival, proliferation, differentiation, and mobilization. The ligands for the protein tyrosine kinase receptors c-KIT and FLT3/FLK2, stem cell factor (SCF), and FL are produced by BM stromal cells and are known to affect several facets of hematopoiesis. We studied another protein tyrosine kinase receptor, c-MET, and its ligand hepatocyte growth factor (HGF), also known as scatter factor (SF), which play a similar role in hematopoiesis. c-MET mRNA is expressed in immature human BM HPCs (CD34+CD33- or CD34+CD38-), but not in more mature HPCs (CD34+CD33+ or CD34+CD38+). The ligand HGF/SF is predominantly produced by BM stromal cells at both the mRNA and protein levels. We confirmed functionally that HGF/SF alone has no effect on proliferation of HPCs, but that when combined with granulocyte/macrophage colony-stimulating factor (GM-CSF) or interleukin-3 it acts as a synergistic proliferative factor, although not as potently as kit-ligand or FLT-3/FLK-2 ligand. Furthermore, HGF/SF promotes adhesion of HPCs to immobilized fibronectin. HGF/SF-induced adhesion to fibronectin is probably caused by activation of the integrins alpha4beta1 and alpha5beta1, insofar as we were able to block this interaction by using monoclonal blocking antibodies directed against these integrin subunits. Addition of the tyrosine-phosphorylation inhibitor genistein inhibited HGF/SF-induced adhesion, supporting the idea that HGF/SF-induced effects are the result of signaling via the receptor c-MET after ligand binding. The enhanced adhesion of HGF/SF to fibronectin proved to be beneficial for the maintenance of the colony-forming potential of HPCs. HGF/SF alone and especially in combination with fibronectin prolongs survival of GM colony-forming cells in liquid culture. Our data indicate that HGF/SF is a polyfunctional cytokine in the BM microenvironment. It is produced by human BM stromal cells and directly or indirectly promotes proliferation, adhesion, and survival of human HPCs.

Bone Marrow Cells↗
PubMed1997

Hepatocyte growth factor/scatter factor promotes adhesion of lymphoma cells to extracellular matrix molecules via alpha 4 beta 1 and alpha 5 beta 1 integrins.

Hepatocyte growth factor (HGF)/scatter factor (SF) is the ligand for a tyrosine kinase cell surface receptor encoded by the MET protooncogene (c-MET). HGF/SF can induce proliferation and motility in epithelial cells and promotes invasion of carcinoma cells and NIH3T3 fibroblasts transfected with both HGF/SF and c-MET genes. Our results show that HGF/ SF and c-MET also play a role in adhesion and invasion of human lymphoma cells. c-MET mRNA is expressed in hemopoietic cells, such as hemopoietic progenitor cells (CD34+ cells) in bone marrow (BM) and mobilized peripheral blood, immature B cells in cord blood and BM, and germinal center B-centroblasts. In normal peripheral blood B cells, which are c-MET-, c-MET expression was induced by PMA, ConA, HGF/ SF, and Epstein-Barr virus (EBV) infection. Using immunohistochemistry, we detected c-MET on the cell surface of large activated centroblasts in lymph nodes from patients with B-non-Hodgkin's lymphoma and Hodgkin's disease. In the latter group, c-MET expression correlated well with the presence of EBV. Because HGF/SF and c-MET promote metastasis of carcinoma cells, we studied the effects of c-MET stimulation by HGF/SF of B-lymphoma cells on properties relevant for metastasis, ie, adhesion, migration, and invasion. HGF/SF stimulated adhesion of the c-MET+ B-cell lines to the extracellular matrix molecules fibronectin (FN) and collagen (CN) in a dose dependent manner. However, adhesion to laminin was not affected by HGF/SF. Adhesion to FN was mediated by beta 1-integrins alpha 4 beta 1 (VLA4) and alpha 5 beta 1 (VLA5) since blocking antibodies against beta 1- (CD29), alpha 4-(CD49d), or alpha 5- (CD49e) integrin subunits, completely reversed the effect of HGF/SF. Furthermore, HGF/SF induced adhesion was abrogated by addition of genistein, which blocks protein tyrosine kinases, including c-MET. Addition of HGF/SF resulted in a sixfold increase in migration of c-MET B-lymphoma cells through Matrigel, compared to medium alone. In rat fibroblast cultures, HGF/SF doubled the number of c-MET+ B-lymphoma cells that invaded the fibroblast monolayer. In these adhesion, migration and invasion assays HGF/SF had no effect on c-MET- cell lines. In conclusion, c-MET is expressed or can be induced on immature, activated, and certain malignant B cells. HGF/SF increased adhesion of c-MET+ B-lymphoma cells to FN and CN, mediated via beta 1-integrins alpha 4 beta 1 and alpha 5 beta 1, and furthermore promoted migration and invasion.

Cell Adhesion↗
PubMed1990

Expression of neural cell adhesion molecule-related sialoglycoprotein in small cell lung cancer and neuroblastoma cell lines H69 and CHP-212.

Monoclonal antibodies (MAbs) 123C3 and 123A8 generated against a membrane preparation of a small cell lung carcinoma (SCLC) specimen recognize not only SCLC and bronchial carcinoids but also a significant portion of non-small cell lung carcinomas (non-SCLC) of various histological types. Together with 13 other monoclonal antibodies, which show preference for SCLC, they have been ranked as SCLC cluster 1 (SC-1) Mabs. In this study we show that SC-1 MAbs are directed against a restricted number of epitopes, and that SC-1 MAbs and a polyclonal antiserum directed against the neural cell adhesion molecule (NCAM) recognize identical glycoproteins, indicating that SC-1 antigens are closely related to or identical with NCAM. Long polysialic acid units composed of alpha-(2,8)-linked N-acetylneuraminic acid units, which in mammals are found exclusively on NCAM, were present on SC-1 antigens in SCLC. This provides further evidence that SC-1 MAbs recognize NCAM. The SC-1 antigens in the SCLC cell line H69 were present in two forms, NCAM-containing alpha-(2,8)-polysialic acid units identified by antiserum 735, the NCAM-H form, and the less sialylated NCAM-L form. The NCAM-H form consisted of diffusely migrating sialoglycoproteins with a molecular weight of 200,000-250,000, which resolved after neuraminidase treatment into two proteins with molecular weights of 140,000 and 180,000. Since the NCAM-H form is expressed in the lung tumor type with a poor prognosis, our results suggest that NCAM might be implicated in the invasive behavior of these NCAM-positive lung tumors.

Antibodies, Monoclonal↗
PubMed1982

Primary health care nurse training in Kwazulu. An evaluation of diagnostic flow charts versus a conventional training method.

Diagnostic flow charts have been adapted for the training of primary health care (PHC) nurses in a rural area of South Africa. We designed a randomized controlled trial to assess whether nurses' clinical competence differed if they were trained using flow charts or using conventional patient-centered teaching. Although clinical competence improved during the training programme, this improvement did not differ significantly according to which of the two training methods was used. The nurses in this trial had considerable earlier experience and some training in primary care. Before the trial they had a high level of clinical competence and may already have developed their own diagnostic strategies. We therefore cannot make inferences from our study about whether or not flow charts will be a valuable addition in PHC. Flow charts need to be adapted to take into account where, by whom, and for what purpose they will be used. They must then be tested to ensure that they only rarely result in incorrect diagnosis and treatment. A decision on the use of flow charts in the training of PHC nurses should be based on further educational trials and long-term follow-up of trained health workers. Nurses should participate in educational trials at the start of their careers in PHC. The additional value of flow charts in the auditing of competence and assessment of educational needs should also be explored.

Ambulatory Care Facilities↗
PubMed1978

Obstetric care in a rural population.

The results of a survey of a rural population requiring obstetric care are presented. It was found that 56,6% of this population had significant risk factors which warranted hospital delivery. A plea is made for the provision of more 'waiting mothers' areas', especially by provincial hospital authorities, to overcome the problems of communication experienced in rural areas. It is concluded that 85% of patients at risk can be detected by meticulous antenatal screening and be admitted to such waiting areas before the onset of labour, with a consequent improvement in perinatal and maternal mortality rates. The need for the provision of adequate postnatal facilities is discussed, and comments are made regarding the implications of the survey with regard to staff utilization.

Adolescent↗