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M Steffen

Publications and source records attributed to M Steffen.

45 records · Page 3Linked to original sources
PubMed1988

Glucocorticoid-induced alterations of morphology and growth of fibrosarcoma cells derived from 7,12-dimethylbenz(a)anthracene rat mammary tumor.

Cloned cell strains with adverse patterns of differentiation obtained from 7,12-dimethylbenz(a)anthracene-induced rat mammary tumor tissue were used to study the effects of glucocorticoid hormones on morphology and proliferation. HH-16 clone 2/1 cells apparently reflecting mesenchymal cells of the stromal part of the mammary gland grow as elongated, mostly bipolar fibroblasts in criss-cross patterns. When cultured in the presence of glucocorticoids, the cells flattened, lost bipolarity, extended in size, and showed arrest of growth at confluence, possibly due to contact inhibition. Immunocytochemical examination of dexamethasone-treated cells revealed actin cables which were absent in untreated cells. The hormone-treated cells expressed Mr 50,000-67,000 cytokeratins, and the extracellular matrix proteins fibronectin and laminin were increased. The in vitro effects on morphology and growth were reversible 3-4 days after withdrawal of the glucocorticoids. In dexamethasone-treated animals the growth of fibrosarcomas produced by inoculation of newborn rats with HH-16 clone 2/1 cells was reduced, and the survival time of the tumor-bearing animals was extended. Apparently, morphology and growth of HH-16 clone 2/1 fibrosarcoma cells can be controlled by glucocorticoids. In comparison, epithelioid HH-16 clone 4 cells established simultaneously from 7,12-dimethylbenz(a)anthracene-induced rat mammary tumor were unresponsive to glucocorticoids.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Simultaneous production of tumor necrosis factor-alpha and lymphotoxin by normal T cells after induction with IL-2 and anti-T3.

Normal human T cells purified from the peripheral blood and cultured for 6 days in the presence of OKT3 and IL-2 were shown to produce simultaneously TNF and lymphotoxin (LT) mRNA. Both biologically active TNF and LT were detected in supernatants of the cultured T cells using WEHI 164 as target cells. The cytotoxic activities of both cytokines could be inhibited with specific antibodies against TNF or LT. The T cell cultures were free of macrophages, NK cells, or B lymphocytes as assessed by flow cytometric analysis.

Antibodies, Monoclonal↗
PubMed1988

Presence of beta-hexosaminidase A alpha-chain mRNA in two different variants of GM2-gangliosidosis.

Tay-Sachs disease displays a variety of forms on the clinical and biochemical level. On the molecular level it has been shown, that poly (A)+ RNA preparations from fibroblasts of patients with classical Tay-Sachs disease lack detectable alpha-chain message when analyzed by Northern blotting with complementary DNA encoding the alpha-chain of human beta-hexosaminidase A. In this report the p beta H alpha-5 clone was used to investigate whether patients with two different variants of Tay-Sachs disease also lack the alpha-chain message. On the basis of RNA hybridization analyses, we could show that our patients which synthesize an altered alpha-chain, as judged by testing enzyme activity and substrate specificity, have the 2.1 kb mRNA which is also seen in healthy control patients.

Cell Line↗
PubMed1988

1,25-Dihydroxyvitamin D3 transcriptionally regulates tumour necrosis factor mRNA during HL-60 cell differentiation.

We investigated TNF-alpha gene expression in HL-60 cells under the influence of 1,25(OH)2D3. Our results show that TNF-alpha gene expression is transcriptionally activated by 1,25(OH)2D3. Despite the increase of TNF-alpha mRNA, very little TNF protein is found in either supernatants or cell lysates of HL-60 cells cultured in the presence of the vitamin. Therefore 1,25(OH)2D3 is regulating the transcription of the TNF-alpha gene in HL-60 cells without affecting translation. Our data suggest that an additional signal is necessary under physiological conditions to control post-transcriptionally TNF-alpha protein synthesis and secretion.

Calcitriol↗
PubMed1987

Identification, isolation, and characterization of a novel cytotoxin in murine cytolytic lymphocytes.

Murine cytotoxic T lymphocytes contain, in addition to the cytotoxic pore-forming protein perforin, another cytolytic factor localized in both cytoplasm and granules. Like perforin, this CTL cytotoxin lyses a variety of tumor cells; unlike perforin, it is stable in the presence of calcium, requires several hours to induce maximal lytic activity, and is antigenically related to the previously described tumor necrosis factor (TNF) and lymphotoxin (LT). However, it differs from TNF and LT in a number of biochemical and functional properties. TNF- and LT-specific cDNA probes did not hybridize with any CTL-specific message, indicating that the CTL cytotoxin is distinct from those two factors. It has an apparent Mr of 50 and 70 kd under reducing and nonreducing conditions, respectively, is secreted by secretagogue-stimulated CTLs, and causes DNA fragmentation in several targets, a phenomenon previously attributed to target cell damage by CTLs. These results suggest that killing by lymphocytes may encompass multiple mechanisms and polypeptides.

Animals↗
PubMed1980

Growth dynamics of a latent primate papovavirus.

The stumptailed macaque papovavirus strain HD was discovered in a persistently infected cell line of primate origin designated Vero 76 (K. Bosslet and G. Sauer, J. Virol. 25:596--607, 1978; W. Waldeck and G. Sauer, Nature [London] 269:171--173, 1977). In clonal derivatives of Vero 76 cells a minor and variable proportion of cells is engaged in the productive synthesis of the HD virus strain. A combination of immunofluorescence using simian virus 40 polyoma subgroup-specific antiserum and in situ hybridization with HD complementary RNA revealed that only those cells which harbor discernible amounts of HD DNA also contain the subgroup-specific antigen. Treatment with arabinofuranosylcytosine caused irreversible disappearance of the antigen, whereas actinomycin D, in contrast, reversibly inhibited both HD DNA replication and synthesis of the subgroup-specific antigen. The proportion of HD DNA and subgroup-specific antigen-synthesizing cells in Vero 76 clonal lines could be either decreased or increased by the mode of passaging of the cell cultures. When cell cultures were split every 3 to 7 days at a 1:4 ratio, the amount of HD DNA sequences as revealed by DNA-DNA reassociation and by the Southern blotting technique fell below the level of detection after only a few passages. Furthermore, expression of the viral subgroup-specific antigen was no longer discernible. However, viral DNA persists in such latently infected cells, because a change in the splitting protocol to a 2-week passaging rhythm led to reinitiation of both viral DNA replication and expression of the subgroup-specific antigen. The HD DNA is perpetuated in a restricted state in latently infected cells in an episomal, unintegrated form as shown by Southern blot analysis. This finding complies with the fact that HD DNA-free subclones could be derived from persistently infected clonal Vero 76 cells. Such subclones have lost the viral genomes, probably owing to segregation during cell division.

Animals↗
PubMedDate not supplied

Experimental realization of Shor's quantum factoring algorithm using nuclear magnetic resonance.

The number of steps any classical computer requires in order to find the prime factors of an l-digit integer N increases exponentially with l, at least using algorithms known at present. Factoring large integers is therefore conjectured to be intractable classically, an observation underlying the security of widely used cryptographic codes. Quantum computers, however, could factor integers in only polynomial time, using Shor's quantum factoring algorithm. Although important for the study of quantum computers, experimental demonstration of this algorithm has proved elusive. Here we report an implementation of the simplest instance of Shor's algorithm: factorization of N = 15 (whose prime factors are 3 and 5). We use seven spin-1/2 nuclei in a molecule as quantum bits, which can be manipulated with room temperature liquid-state nuclear magnetic resonance techniques. This method of using nuclei to store quantum information is in principle scalable to systems containing many quantum bits, but such scalability is not implied by the present work. The significance of our work lies in the demonstration of experimental and theoretical techniques for precise control and modelling of complex quantum computers. In particular, we present a simple, parameter-free but predictive model of decoherence effects in our system.

Journal Article↗