Search PubMed⌕ Search

Biomedical subjects

D Soll

Publications and source records attributed to D Soll.

9 recordsLinked to original sources
PubMed1992

Targeted disruption of the ABP-120 gene leads to cells with altered motility.

The actin-binding protein ABP-120 has been proposed to play a role in cross-linking F-actin filaments during pseudopod formation in motile Dictyostelium amebas. We have tested this hypothesis by analyzing the phenotype of mutant cell lines which do not produce ABP-120. Two different transformation vectors capable of targeted disruption of the ABP-120 gene locus have been constructed using a portion of an ABP-120 cDNA clone. Three independent cell lines with different disruption events have been obtained after transformation of amebas with these vectors. The disruption of the ABP-120 gene by vector sequences results in either the production of a small amount of truncated ABP-120 or no detectable protein at all. The phenotypes of two different clones lacking ABP-120, generated in strains AX3 and AX4, have been characterized and show identical results. ABP-120- cells tend to remain rounder before and after cAMP stimulation, and do not reextend pseudopods normally after rapid addition of cAMP. In addition, ABP-120- cells translocating in buffer exhibit defects in both the rate and extent of pseudopod formation. The amount of F-actin cross-linked into the cytoskeleton after cAMP stimulation of ABP-120- cells is reduced at times when ABP-120 has been shown to be incorporated into the cytoskeleton, and this correlates temporally with the absence of reextension of pseudopods after cAMP stimulation. The instantaneous velocity is significantly reduced both before and after cAMP stimulation in the ABP-120- cells, and the cells show decreased chemotactic efficiency compared to ABP-120+ controls. This phenotype is consistent with a role for ABP-120 in pseudopod extension by cross-linking actin filaments as proposed by the "cortical expansion model" (Condeelis, J., A. Bresnick, M. Demma, C. Dharmawardhane, R. Eddy, A. L. Hall, R. Sauterer, and V. Warren. 1990. Dev. Genet. 11:333-340).

Actins↗
PubMed1987

Increased cytotoxicity of 1-(2-chloroethyl)-1-nitroso-3(4-methyl)-cyclohexylurea by pretreatment with O6-methylguanine in resistant but not in sensitive human melanoma cells.

Cells from a resistant ("Gr II") and a sensitive ("Str") human melanoma xenograft were incubated in vitro with O6-methylguanine for 2 h, subsequently treated with 1-(2-chloroethyl)-1-nitroso-3(4-methyl)-cyclohexylurea (MeCCNU) for 1 h and then plated in soft agar. In the resistant cells the O6-methylguanine pretreatment (2 mM) yielded an increase in sensitivity towards MeCCNU by a factor of 7.5. In the sensitive melanoma cells pretreatment with O6-methylguanine did not increase cytotoxicity. Human bone marrow cells from three normal donors were similarly pretreated with O6-methylguanine and MeCCNU. There was a clear increase in MeCCNU-induced cytotoxicity. We conclude, that while O6-methylguanine does potentiate the action of MeCCNU in resistant melanoma cells, the therapeutic usefulness of this treatment strategy may be limited.

Animals↗
PubMed1986

Enhancement of etoposide-induced cytotoxicity by cyclosporin A.

Following the clinical observation of enhanced antineoplastic action of etoposide in the presence of cyclosporin A (CyA), we investigated this drug interaction in several in vitro and in vivo tumor systems. Macromolecular DNA damage induced by etoposide at drug levels comparable to plasma AUC values achieved in patients was increased not only in leukemic peripheral blood cells from patients but also in mononuclear peripheral blood cells from a healthy donor. Intracellular retention of radioactivity from 3H-etoposide was increased by a factor of 1.5 at the most in the presence of CyA. The cytotoxicity of etoposide and adriamycin to L 1210 leukemic cells was clearly enhanced, whereas CyA had no effect on the action of cisplatin or ionizing irradiation. At CyA blood levels not exceeding 1.44 microgram/ml, increased tumor inhibition of etoposide was observed in a human embryonal cancer xenograft, but there was also higher lethality in normal mice. We conclude from our own data and from other recent findings that with respect to chemosensitization the effects of CyA resemble those of calcium channel blockers or anticalmodulin agents. In contrast to calcium channel blockers, however, adequate plasma levels of CyA can well be achieved in patients.

Animals↗
PubMed1976

The nucleotide sequence of asparagine tRNA from Escherichia coli.

The nucleotide seuquence of Escherichia coli asparagine tRNA was determined to be pU-C-C-U-C-U-G-s4U-A-G-U-U-C-A-G-D-C-G-G-D-A-G-A-A-C-G-G-C-G-G-A-C-U-Q-U-U-t6A-A-phi-C-C-G-U-A-U-m G-U-C-A-C-U-G-G-T-phi-C-G-A-G-U-C-C-A-G-U-C-A-G-A-G-G-A-G-C-C-AOH. Its D-stem and D-loop have almost the same sequence as Escherichia coli aspartate tRNA.

Asparagine↗
PubMed1974

Sequence studies of nonradioactive Mycoplasma tRNA Phe with the aid of polynucleotide phosphorylase and polynucleotide kinase.

The known methods of enzymatic phosphorylation with [(32)P]phosphate of the 3'- or 5'-hydroxyl group of an oligonucleotide have been applied to oligonucleotides derived from Mycoplasma tRNA(Phe). The fingerprints obtained by both methods are very similar to each other and to that of uniformly labelled tRNA. The sequence of some oligonucleotides was determined by partial digestion of the 3'-phosphorylated fragment with spleen phosphodiesterase and of the corresponding 5'-phosphorylated fragment with venom phosphodiesterase.

Base Sequence↗
PubMed1974

The nucleotide sequence of phenylalanine tRNA from Mycoplasma sp. (Kid).

The nucleotide sequence of Mycoplasma sp. (Kid) phenylalanine tRNA was determined to be pG-G-U-C-G-U-G-U-A-G-C-U-C-A-G-U-C-G-G-D-A-G-A-G-C-A-G-C- A-G-A-C-U-G-A-A-m(1)G-C-Psi-C-U-G-C-G-U-m(7)G-U-C-G-G-C-G-G-U-Psi-C-A-A-U-U-C-C-G-U-C-C-A-C-G-A-C-C-A-C-C-A(OH). It is characterized by the absence of ribothymidine and the presence of only few modified nucleotides.

Alkaline Phosphatase↗
PubMed1974

The phenylalanine tRNA from Mycoplasma sp. (Kid): a tRNA lacking hypermodified nucleosides functional in protein synthesis.

Phenylalanine tRNA from Mycoplasma sp. (Kid) was purified and characterized. The tRNA can be aminoacylated by phenylalanyl-tRNA synthetase from both Mycoplasma and E. coli. In a tRNA-dependent cell-free E. coli amino acid incorporating system programmed with poly U pure Mycoplasma tRNA(Phe) was fully active in promoting phenylalanine incorporation, even in direct competition with homologous E. coli tRNA(Phe). Since the Mycoplasma tRNA lacks isopentenyladenosine, or any related hypermodified nucleoside, it appears that the presence of such nucleosides in tRNA is not an absolute requirement for protein synthesis.

Adenosine↗