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Biomedical subjects

I Pastan

Publications and source records attributed to I Pastan.

At least 793 records · Page 44Linked to original sources
PubMed1971

Restoration of several morphological characteristics of normal fibroblasts in sarcoma cells treated with adenosine-3':5'-cyclic monphosphate and its derivatives.

Sarcoma cells growing in tissue culture have morphological and growth characteristics different than normal fibroblasts. Several of the morphological characteristics of normal fibroblasts are regained when the cells are incubated with dibutyryl-cyclic AMP or butyryl-cyclic AMP (0.1-1 mM), or cyclic AMP (3 mM) plus theophylline (1 mM), but not with ATP, ADP, AMP, adenine, or adenosine (1-7 mM). The cell bodies become elongated; distinct narrow processes are formed. With prolonged incubation, the cells show less tendency to pile up or become polygonal. Further, L-929 and Rous sarcomatransformed hamster cells orient in parallel arrays characteristic of contact inhibition. The cells retain their altered morphology as long as the butyryl-cyclic AMP is present, but revert after its removal. Experiments with cycloheximide, puromycin, and actinomycin D indicate that protein Synthesis, but not RNA synthesis, is required for the response. Microtubular proteins may be involved. No response is observed with normal fibroblasts or with various epithelial cells. The data suggest that cyclic AMP may be an important factor in the determination of morphology of normal fibroblasts and this function may be lost or altered during transformation.

Adenine Nucleotides↗
PubMed1971

Isolation of the gal repressor.

The repressor of the galactose operon of Escherichia coli has been partially purified and identified as a protein. Induction of a lysogen in which lambda was linked to the bacterial galR and lysine genes resulted in a large increase in the production of the gal repressor. Single-step purification by affinity chromatography, using the ligand p-aminophenyl-beta-D-thiogalactoside linked to beaded agarose, provided a convenient method of separating the gal repressor from other DNA-binding proteins. Binding of gal repressor to lambdapgal[(32)P]DNA was studied by assay of binding to a nitrocellulose filter. Interaction between gal repressor and lambdapgal DNA showed a high degree of specificity; the dissociation constant of the complex was estimated to be 1.0 x 10(-12) M. Unlabeled lambdapgal DNA competed for binding to gal repressor, but lambdaDNA and lambdah80dlac DNA did not. Fucose and galactose, which function as inducers of the galactose operon in vivo, produced one-half maximal inhibition of gal repressor-lambdapgal DNA binding at concentrations of 5 x 10(-5) M.

Chromatography↗
PubMed1971

Analysis of the fusion of XC cells induced by homogenates of murine leukemia virus-infected cells and by purified murine leukemia virus.

The fusion of XC cells induced by murine leukemia virus (MuLV)-infected cells is also induced by homogenates prepared from the infected cells and by purified MuLV. The fusion-inducing factor appears to contain a heat-labile lipoprotein. No synthesis of specific macromolecules by the XC cells is necessary to obtain fusion. The results suggest that specific components of the viral particle are the activators for the fusion process and they may also be present in the membranes of infected cells.

Animals↗