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Biomedical subjects

S Leffler

Publications and source records attributed to S Leffler.

24 records · Page 2Linked to original sources
PubMed1974

Interaction of Escherichia coli 30S ribosomal subunits with MS2 phage RNA in the absence of initiation factors.

MS2 RNA binds at 0 degrees to 30S subunits from E. coli and, to a smaller extent, to those of a Pseudomonas species, as judged by filtration on nitrocellulose membranes; this mRNA does not bind to 30S subunits from Bacillus brevis or Caulobacter crescentus. Binding does not depend on the presence of initiation factors; it is sensitive to aurintricarboxylic acid but insensitive to edeine and is competitive with such synthetic polynucleotides as poly(U) and poly(AUG). Complex formation can also be detected by electrophoresis on polyacrylamide-agarose gels. By this procedure, E. coli 30S subunits are separated into two major components. Only the more slowly moving component, which contains the ribosomal protein S1, interacts with the RNA.

Anti-Bacterial Agents↗
PubMed1973

Messenger selection by bacterial ribosomes.

The counterpart of Escherichia coli initiation factor 3(IF-3) was isolated from Caulobacter crescentus, purified to homogeneity, and used in comparative studies on in vitro translation of RNA from the C. crescentus RNA phage Cb5 and of coliphage MS2 RNA. The two phage RNAs are similar in physical properties and analogous in genetic content. The factor, C-IF-3, substitutes for E. coli IF-3 and promotes correct translation of MS2 RNA by E. coli ribosomes. Conversely, E. coli IF-3 substitutes for C-IF-3 in translation of Cb5 RNA by C. crescentus ribosomes. However, each phage RNA could be translated only by host ribosomes or by mixed ribosomes containing the host 30S subunit. C-IF-3 dissociates C. crescentus and E. coli 70S ribosomes into subunits. It binds phage, ribosomal, and, less efficiently, transfer RNA.

Amino Acids↗
PubMedDate not supplied

Contrast-enhanced MR imaging of diffuse and focal splenic disease with use of magnetic starch microspheres.

The diagnostic value of magnetic starch microspheres (MSM), a new superparamagnetic contrast agent, was studied in experimental models of diffuse and focal splenic disease in rats by means of ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Owing to small differences in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor-bearing animals from control animals by signal-to-noise ratios (SNRs) obtained with T1- and T2-weighted spin-echo sequences. One hour after injection of 20 mumol/kg MSM, lymphomatous spleen showed significantly (P < .001) reduced enhancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 +/- 1.7) could be easily differentiated from control animals (SNR: 5.5 +/- 0.6) on T2-weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enhancement of nontumorous splenic tissue, whereas relaxation times of tumors were not different before and after contrast agent injection. On T2-weighted images (2,000/45), the tumor-spleen contrast-to-noise ratio increased from 4.8 +/- 1.6 to 21.8 +/- 1.9 (+354%), improving conspicuity of splenic tumors. The results show that MSM-enhanced MR imaging improves the detection of diffuse and focal splenic disease.

Animals↗